Medical treatment in Ecuador is significantly less expensive than USA, and therefore so is health insurance. However if your son intends to travel around REcuador he ought to be aware that medical facilities outside the major cities are poor or non-existent. There is no hospital on the Galapagos islands, and alarmingly for a popular scuba diving spot, no decompression chamber. Medical emergencies on the islands require evacuation - which can be very expensive.
Also, Quito which is situated at 2800 metres above sea level causes many visitors 'altitude sickness', and unfortunately decompression chamber facilities are limited, an again medical evacuation would be needed.
Malaria and Dengue Fever is widespread in Ecuador. These diseases often don't show up until after the traveller returns home.
For all these reasons I strongly recommend your son have adequate TRAVEL INSURANCE in addition to any health insurance he takes out in Ecuador. Phil almost 9 years ago