It's a good idea to watch the behavior of the vehicles around you carefully - but don't necessarily follow their lead. If the vehicle ahead speeds through a stop sign without slowing - go ahead and stop anyway.
It's a good idea to drive at or below the speed limit, which will be shown (in most places) in kilometers. The easy conversion is that 100kph = 60mph, so if you see that speed posted, drive at around 55mph. In the US it's common to "push" the speed limits; in Mexico it's advisable to hold back a little. This will mean driving through some small towns at 15 mph.
Have a reliable road map with you. ''GuiaRoji'' is a good option, but there are also others that are just as good if not better. Your first stop in Mexico should be to pick up a map. When planning your route in Mexico, remember that a straight line is not always the best way from point A to point B. [http://www.cochera-andina.com cochera andina] provides information about road conditions, travel times e.g. for more than 240 routes in Mexico. If you haven't driven in Mexico before, stick to the toll roads.
Much of Mexico is covered by modern "Cuota" Toll Roads, most of these are privately owned. They are generally preferable to the free "Libre" roads, if the latter run parallel. If you are planning on making a long drive on toll roads, make sure you have plenty of Mexican pesos with you. U.S. dollars and credit cards are NOT accepted. Using toll roads in Mexico is quite expensive: the tolls range from about 25 to 150 Mexican pesos (approx. 2.50-15 USD) for passenger cars, depending on the section of highway. The price only goes up if you're in an RV or towing something. Also, there can be several tollbooths between cities. Even with the prices of using Mexican toll roads, some are not in conditions one would expect for the price you pay to use them. Some are in need of resurfacing, and will abuse your car if you travel the speed limit (which is normally 110 kph). It is a good idea to travel these sections of road under the speed limit to make sure your car makes it back up north without any suspension or other issues. If the conditions of the toll road cause damage to your vehicle (including blow-outs), insurance is included in the price of the toll (make sure to keep your toll payment receipt). This does not include an accident with another vehicle. (Your Mexican car insurance covers that.) Damage caused to your car has to be reported immediately at the next tollbooth you come to. It would be a good idea to take note of the "kilometer" marker where the incident happened, and have all of your papers ready (including toll receipt). If your only loss is a tire, and you're in a hurry, you may not want to bother making a claim since it can take some time. Some very fluent Spanish is also a strong recommendation, since most employees working the toll roads may not speak enough English to process a claim.
A plus for toll roads is that there are clean bathrooms and snack shops at most toll booths. It's a good opportunity to stretch your legs a bit, have a bite to eat, or visit the restroom before continuing on your way.
Once you get off the main highways, it's common to find potholes, dropoffs, dirt roads, and other hazards. The Mexicans brave these in standard passenger cars, but you'll probably be more comfortable in a higher-clearance vehicle such as an SUV, especially if you plan to visit hot springs, beaches, camping areas, or other off-the-beaten-path locations.
The Mexican Federal Police (Policia Federal or "Federales") patrol the roads. Unfortunately, the culture of "mordida" (the form to say bribe in the local slang) still prevails, and as often as not the Federales may be willing to let you off with a warning in exchange for some folding money. However, do not by any means assume that the officer is expecting a bribe - some are well aware that it is illegal, and they will be offended or may even arrest you for offering! As in most places, courtesy and respect are most important. Knowing Spanish is also very useful in these situations, since the police are not expected to know English.
Insurance in Mexico is not mandatory but highly advisable, so don't leave home without it - it can be purchased online, or in offices near the border. Insurance should cost less than $10 per day. If you are in an accident and you don't have insurance, you could have trouble with police. Sanborns and Gieco both offer pretty good insurance, check out [http://www.drivetheamericas.com/wiki/Your_Vehicle Drive the Americas] this site has some good info if you're thinking about driving the Pan American Highway. [http://www.e-ici.net Insurance Consultants International] and [http://www.car-insurance-for-mexico.com Mex Insurance Online] are excellent sites where you can buy Mexican insurance for your car with just a click.
In my 40 years of driving Mexico, I've used and worked with several companies. When buying Mexican auto or RV insurance it is important to compare. Good companies today include legal aid and some bundle medical air evac, which is superfluous, since medical care in Mexico is excellent. While the above quote of $10 is a general guideline, it is cheaper with any carrier to purchase a 6 month or annual policy if your trip covers more than 16 days. Something else to consider is will the company fix your car in the United States as well as Mexico. Do they offer any trip advice? I worked in the Mexican insurance industry for a decade and sadly, companies change. A good company a few years ago may not be so good now. Also, if your trip is only for the Baja or Sonora, region-specific policies are a better deal. Beware of any company selling the cheapest policy. You get what you pay for. The above site is reputable, but for a comparison of three of the best, I stay on top of changes in quality of service and delete some when their service declines. See also Mexicomike.com [http://www.mexicomike.com Mexico Mike] for comparisons.
The Mexican government operates a roadside assistance program called the "Angeles Verdes" or "Green Angels". The green trucks and their operators have the wherewithal to fix many debilitating automobile conditions. In fact, many travellers who have benefited from their services consider them miracle workers - did you know you can fix a leaking radiator with pepper, or an egg? Services and information are free; parts or gasoline if necessary must be paid for.
In Mexico, they're serious about speed control. "Topes" or speed bumps often consist of a large steel pipe with small asphalt ramps.
When driving cross-country, you will often encounter "vados" or dips. These are generally places where a stream or other feature crosses the road, and often they are severe - slow down and keep your eyes open. Cattle tend to congregate in vados.
When on steep, narrow or single lane roads, the downhill traffic has the right of way over uphill traffic. If you are going uphill and you see oncoming traffic, pull over to the side of the road, well out of the way and either slow down or stop. If you are going downhill, use caution as the driver may not have read this.
Interesting point. From a practical standpoint, it is wise to keep an eye out for pullouts. The closest one may be behind you. This tip applies only to some really out-of-the-way roads, as there are few of these old roads left.
A practical tip for mountain driving is to keep your cool. If you get behind a big truck on a narrow 2 lane road, do not try to pass on blind curves. Have patience. Eventually, there will be a pullout or slightly wider section where it will be safe to pass. For this and other tips about driving in general see my tips section -- [http://www.mexicomike.com/driving/driving.htm Mexico Driving Tips.]
One situation that you will probably never see (I've only encountered this twice in 40 years) is if you see a sign with arrows pointing to the opposite side of the road (as well as arrows painted on the road), they are telling you to move to the OPPOSITE lane, i.e. drive on the left as in England. The idea is the car going uphill should move to the outside lane. Scary, but if you don't, it could be disastrous. That said, the likelihood of most people to be on a road like this is pretty slim.
Expect checkpoints along most major and some minor roads, manned by the Mexican military - mostly with automatic weapons. You will be asked for driver's licence and insurance information. Your vehicle will be searched, with varying degrees depending upon your attitude, your load, and how bored they are. They are looking for drugs or weapons which you should not have with you.
They do not expect (or accept) bribes of any sort - but cold non-alcoholic beverages are often appreciated.
At military checkpoints you will never be asked for identification. The army has no right to do so and I have never been asked in 40 years.
Many guidebooks and travellers advise against driving at night. This is excellent advice. When driving the "libre" roads at night you will likely encounter pedestrian traffic (people on the way to church, every night}, animals, slow moving traffic, road hazards and the occasional person who has fallen asleep on the warm road or is simply just sitting there. Driving at night, outside of a municipality, tourist area, or on a toll road is risky and dangerous. There are some Mexicans who (perhaps to save fuel?) drive without lights; drunk driving is very common at night.
I beg to differ with the above advice. It is outdated. The reason you have auto insurance is to keep from going to jail. I have had accidents and know this. What the author above is referring to is that in the case of a death or serious injury, the drivers are expected to stay until it is sorted out. For gringos, that means staying in a hotel, not jail. Your insurance adjuster is there to protect your rights and should be called immediately after an accident.
I have been helped by so many Mexicans who have stopped to help me that it seems chauvinistic to not stop and help others. In nearly 40 years of driving Mexico, I have never seen a bandito.