The food in Costa Rica is not very varied. The national dish is the gallo pinto (literally "spotted rooster"), rice n' beans made in coconut milk. For lunch they have the casado, rice and beans again, accompanied with tomato salad, fried plantains, and meat. In many bars drinks are served with small amounts of food called bocas. The most popular are ceviche (raw marinated fish), chicken wings and bean soup.
Costa Rica is also famous for its coffee, but the best beans are exported. The number one local beer is Imperial, which tastes great. My favorite drinks were the fruit shakes with tropical fruits. Tap water is not safe for drinking. Always buy bottled water.