Barbados, Grand Cayman or Puerto Rico come to mind as possibilities, but I can't speak to Hilton or Marriott properties specifically.
We really enjoyed Barbados, especially the diving/snorkeling, good food and Mt. Gay rum tour (and the happy hour at Castaways in St. Lawrence Gap was the best). Grand Cayman is great if you're looking for beaches, water activities and good food. I've also heard that the El Conquistador in Puerto Rico is a great getaway spot.