I was going to suggest Dominican Republic, we have been there twice, but it was in december. Both times we stayed on the North coast near Puerto Plata. One time in Camino del Sol, and the other time in Riu Merengue. We had a lot more fun in Camino del Sol! Stay away from Sosua!
Dominican Republic is quite cheap compared to the rest of Carribean and there are so many things to see and the locals are really friendly. I don't recommend that you hire a car!
Here' s a link with reviews of various places and hotels:
http://www.debbiesdominicantravel.com/
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