virtually all south american doctors I've encountered are excellent. My broken and repaired elbow tends to agree.
irrespective of the question how high the level of education is at the uni of havana, it only would be about 4months and I'm going to make my degree in Germany anyway... would you be happy with a German-educated surgeon who broadened his horizon?
I cannot comment on how an HR person would view that experience, because HR thinking makes absolutely NO sense to me. But if I were a hiring manager, I would look very favorably on that level of diversity in an applicant's background. This is perhaps even more true in trading.
Before venturing off to Cuba, what is wrong with London School of Economics? Is Cuba a choice because you cannot get into a good school in London which is more of a financial center than Havana. The discussion above on medicine is besides the point. If you want a good education on finance, you got a ton of good schools right in your backyard. If you want to chill on a beautiful island then studies might not be the first priority.