you can catch a bus from the capitol for $4-5. and it will be an adventure I am sure, becareful of Pick Pockets at the Coca-cola bus terminal in San Jose.
You can also rent a car I would recommend a 4 wheel drive. the roads are not well marked and very curvy and winding with steep cliffs at times
there are 2 types of busses, the express or the collectivo. they cost the same. 25 cents, maybe a bit more now.
Taxis are available. they will sometimes try to charge the ignorant tourist more. but if you know what to expect they will be reasonable.
There is a lot to do in Costa Rica, the canopy tours are not to be missed. there is White water rafting, sea kayaking, sunset sail, you can rent jet ski's from the beach, and of course surfing.
The locals are friendly and helpful if you ask.
You can eat for Cheap or not. A very filling and tasty meal can be had for $2. If you check out the hole in the wall restaurants.
The nice hotel/resorts have all the old standards for more $.
I would recommend trying the Batidas, fruit smoothies made with fresh fruit. They usually will add sugar unless you order it "sin asucar" or with 'no sugar'.
Also the pipa frio, coconut, green variety, they chop the top off and add a straw, this stuff is better than Gatorade for re hydrating you, it's incredibly healthy. You might not like it at first, but it grows on you and is cheap!