Aruba gets my vote for the best Caribbean vacation island, but if you can't take the heat, stay out of this kitchen. But with the help of the consistently brisk winds and a beach umbrella you can hold your own. Personally I would go out and run in the heat and jump into the pool afterwards. Yeah, I'm nuts that way.
Aruba is Dutch and its location just north of Venezuela brings in Spanish influences. English is spoken everywhere, unlike some other islands. For a chillaxing vacation, check it out.