Don't expect to cash personal checks. Major credit cards are accepted in most large stores or hotels in the larger cities. When you get to school, you may ask where is the best and fastest way to change money. Public health in Costa Rica compares favorably with that of many developed countries. No shots are necessary to come to the country.
Medical facilities are numerous and dependable.
Unlike other Third World countries, it is safe to drink the water. Costa Rica, in general, is a safe place. Most crime is the petty type. Don't leave valuables or personal documents unattended or in a parked car. Buses are widely used and economical.