Most hotels in Costa Rica offer a buffet for breakfast and dinner. The buffets are likely to contain the following items or similar:
Breakfast:
cereal, bread, cake, pastries, coffee, juice (sometimes from a machine), bacon, eggs, gallo pinto (rice and beans) a range of yogurt, fruit etc
Evening meal:
rice, beans, plantain, vegetables, salads, meat (options including one or more of chicken, beef, pork - worth noting this might be in a sauce), fish, bread, soup. Water and fruit juice.
Last year, the buffet arrangements offered vegetarians a good choice of food. Those with dairy intolerances found the buffets worked well for them to choose from although there often wasn't a range of dairy-free milk available so you might want to buy some in San Jose to take with you. Please note that we didn't have any guests who were coeliac or with severe allergies so (although generally well-labelled), we wouldn't have been confident about cross-contamination. It is worth bearing in mind that the staff may not always speak good English and the hotels may not be used to considering cross contamination, for example.