I'll second St Vincent and south. Very unspoiled. Diving was spectacular. Provisioning can be difficult. Last time I was there we found a small yacht provisioning service on Bequi that had freezers full of anything you could want. It is deffinatly open ocean sailing between the islands and very windy.
Cruising in Belize is some what limited to inside the reef. While we didn't have a problem there is a lot of poverty. Reefs were very alive w/ coral but no fish. Discovered why at the airport when we saw countless foam coolers labeled "live tropical fish".
Bahamas are too developed for my liking on vacation but very safe.
Haven't been back to Turks and cacos in 30 years but would guess they are like the Bahamas now.
S/V Deja Vu