Blondie is right about Jamaica. It is very beautiful but very corrupt and you can not (or should not, rather) leave the resort unless you are on a resort sponsored outing.
I went to Cabo San Lucas, Mexico and had a BLAST. I loved it. I think I love Mexico so much because I know their culture so well (living in So Cal) and I don't feel out of place there. The food is great, the drinks are better, and the place I stayed at was gorgeous. I'll find the name if you want it. It was right in the middle of everything... There was a "Fiesta" in the name...
EDITED TO ADD: Another thing about Jamaica this time of year is it's hurricane season and it's HUMID. We went in July. Mexico will be hotter than the face of the sun, but at least it won't be humid.