Tamarindo has the best health services of any beach town on the northwestern coast of Costa Rica. Only ten years ago, there was not even a pharmacy! It had one unofficial doctor and no dentists. Now, Tamarindo has an ambulance service, several Costa Rica certified doctors and dentists, and 4 pharmacies. On a regular basis, the clinics have visiting specialists for such things as skin disorders, physcology, etc. Tamarindo also has it's own small airport that has been a lifesaver for those in more serious trouble. Compared to other beach towns, Tamarindo has far more health services. 

Just outside Tamarindo, and hour's drive away are the regional medical clinics in Liberia and Nicoya. The big hospitals are in the capital in San Jose which is a 5-hour drive, but only 45-minutes from the Tamarindo Airport. They are famous for providing world-class care at a fraction of the cost of the USA.

Don't visit Tamarindo, or any beach community in Costa Rica, if you have a life-threatening illness, it could be several hours before arriving at a major hospital. All of them are located in the capital which is in the center of the country in San Jose. 

The two main safety concerns are riptides and Dengue Fever. Never swim alone and take precautions against being bitten by the Dengue mosquito.

All in all, Tamarindo is a healty place to visit and live. Confirmation is that more families than ever have move to Tamarindo and the town has been enjoying a "baby boom" among locals during the past few years.  

More health-related info can be found here:

Costa Rica Illness

Info on Dengue fever from the U.S. Center for Disease Control