Comida tipica or native dishes, rely heavily on rice and beans, the basis of many Costa Rican meals. Home-style cooking predominates. But meals are generally wholesome and reasonably priced. Gallo Pinto, the national dish of fried rice and black beans is particularly served as a breakfast. Notable is the famed Rice n' Beans of the Caribbean, a Gallo Pinto made in coconut milk, worth trying.
Many meals are derivatives, including arroz con pollo or arroz con atun.
Vegetables do not form a large part of the diet. Costa Rica home cuisine has an inordinately ammount of fried foods so keep that in mind when you receive and invitation for dinner. Travelers with low budget should stick with the casado on lunch time menus, or 'plato del dia' which is a close cousin of the casado with a common denominator of low price and varied ingredients. Eating in Costa Rica doesn't present the health problems that plague the unwary traveler elsewhere in Central America, but you need to be aware that some of the pesticides used in Costa Rica are forbidden elsewhere. Something I should say is that you may eat where the locals eat, usually that means tasty and trustworthy food.