If you are driving simply take the Pan American highway east towards San Miguel and turn right at the Mercedes intersection.
The city also celebrates the Semana Santa(Holy Week) with parades and by making traditional alfombras(rugs) depicting scenes from the resurrection out of colored salts as well as whatever is available at the time.
There is also a year festival to celebrate the patron saint of Berlin, San Jose. Check Berlin's webpage below for the exact dates of these events.
The hike up the "Cerro de la Cruz" takes about 45 minutes to an hour and is of medium difficulty. Without a guide to the top it may be difficult to find your way. Many local children will jump at the opportunity to show you the way, and are especially great for pointing out different fruits and other plants. Tip them or take them for ice cream afterwards.
It's a favorite spot among El Salvadorans and its common to see locals trekking out hunks of the clay which they use for medicinal purposes. There are several picnic tables and large rocks to congregate around. The laguna itself is only deep in the very center although most El Salvadorans will not swim in the laguna. There is a myth that a mermaid lives in the laguna which drowns handsome young men. The myth likely originates from the sticky clay bottom and the fact that many El Salvadorans are poor swimmers.
Take the bus from Berlin that leaves every 45 minutes for Santiago de Maria next to the City Hall. Ride the bus all the way through the lovely town of Alegria and exit on the opposite side of the town near a cobblestone path with a bus stop next to it. The roud is roughly 1.5 miles long and is a moderate hike through coffee plantations. The road will end at the entrance to the laguna and a small tienda is located just to the left of the entrance. Admission is 25 cents for the day.
If you're in decent shape and feel like a real challenge you can take a great hike from Berlin up to the very lip of the crater. Simply follow the same road up the hill you take to go to the Cerro de la Cruz near the community called Brisas del Sol. Instead of splitting off to go to the cerro continue on the road and it will pass by a steaming volcanic crater, a large soccer field with a great big tree and sitting rocks for a break, and then through a coffee finca called Optimismo and finally end up at a small military installation. You will then take a trail to the right along the rim of the crater which eventually descends to the entrance to the laguna. It can be somewhat challenging at times but the views are spectacular.
Pupusas are prevalent as well as numerous french fry vendors around the park. Because of its high altitude all of the papusas are made with corn flour. A small blue stand half a block down from the north west corner of the park sells papusas with green onions.
Other cheaper options include the Hotel Berlineses which is $10/room and also has small restaurant attached and even a very shallow pool. The Hotel is a block down the hill from the northwest corner of the park.