I don't know about cuba specifically, but for a majority of conditions most major cities in the world have good, modern medical care available. I have first-hand experience of this on at least seven countries on three continents just on incidental medical needs, and know others who have described much the same experience in several countries I've never visited. Compared to the US, prices are quite low across the board, even for non-citizens who have to pay out of pocket, due to the unique way the various US industries involved in healthcare have dramatically driven up prices. Medical tourism is sometimes even worth it for people who have insurance.