Sorry to disagree, but Belize is far safer than most american cities. Many places to cruise, even more to dive. The water is wonderful and I found the people to be very nice. Some areas are too americanized and the people resent them for doing so.
Bahamas are nice too, perhaps a bit more shallow water and tougher sailing depending on your route. More "american" style provisions but more $$, but like belize water can be pricey so don't waste.
Best of luck where ever you go.