I would promote Utila an island off of the coast of Honduras, beaches aren't really great but it is one of the top spots for diving and it is quite cheap and most of the locals speak English. On the other hand it is in Honduras and right now on the coast you could also have a very exciting vacation with roadblocks, rioters and maybe some tear gas.
http://coralbeachvillage.com/utila-isla-de-bahia-the-authentic-island-experience-still-exists/