Sao Vicente - There are much better medical facilities on Sao Vicente than on Sal.
Santiago - Although Santiago is the capital, it's medical facilities are not as good as that on the island of Sao Vicente.
Boa Vista There is a new hospital. There is only one main town there called Sal Rei which isn't that big. The villages are smaller so there hasn't been the need for a major facility on the island until some larger hotels were built to accommodate more tourists.
Santo Antao - The hospital in Ribeira Grande I am told is quite good.