No shots are necessary to come to the country. Medical facilities are numerous and dependable. Many English speaking doctors and dentists practice in San Jose. 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 aparked car. Buses are widely used and economical. Most taxi fares within San Jos are relatively inexpensive. Travel by air within the country is adequate and inexpensive. You may drive up to 3 months with a valid drivers license issued by your country.