Jamaica sucks. I will never give another penny of my money to the welfare/thief types that live there. Their mindset is white people = money...that's all you are to them. Anywhere armed guards have to walk with you a block to the store is not where I need to be. Been all over Jamaica on two different trips (Negril, Montego, Ocho Rios, etc), and it was that way everywhere I went. I'm a pretty big dude, but I had knives pulled on me two times and cocaine (probably fake) shoved into my pocket on the street multiple times. If the rasta guys force drugs into your pocket and then try to extort money out of you, you can normally get rid of them bn\y pulling the drugs out of your pocket, holding it over your head, and yelling "No, I don't want your drugs!" The cops typically run to you quickly and haul away the nappy headed douches. Don't ever let your guard down anywhere in Jamaica, unless you are at one of the all-inclusive resorts on the beach that have armed guards posted around the premises. These resorts keep most of the bums from bothering you on the beach, and they require that an armed guard walks with you if you go off-premises to the store, etc.
Just got back from a trip to the Keys a couple weeks ago. I spent 4 nights in Key Largo/Islamorada and 2 nights in Key West. First, there are no all-inclusive type places there, and there aren't many traditional beaches. There is a pretty nice beach at Bahia Hondo between Islamorada and Key West, but most any beach you find at a hotel south of Islamorada is man-made and small. Islamorada is a great place for fishing...lots of guides and good catches. At Robbies in Islamorada you can feed tarpon at dockside while waiting for your breakfast, and it's a ton of fun. They'll take the fish out of your hand, and I had one take in my entire arm almost to my elbow.
If you like to snorkel/dive, Pennekamp park in Key Largo is one of the best in North America. Key West is the party place. Bars, restaurants, and shops everywhere. We had fun at Captain Tony's and ate very well while we were there. I wasn't overly impressed with the Keys until we got south of Key Largo, and it all changed. You don't start humming Buffett songs until you hit Bahia Hondo on the way down to Key West.
I would definitely go back to Key West and Islamorada.
I've been to about 1/3 of the islands in the Caribbean, and there are some awesome places to visit. My personal favorite was Antigua. The people there are extremely friendly and appreciative of your travel dollars. There is a very good reason Clapton makes Antigua home.
Others I've been to and would go back again are St. Lucia, Barbados, and St. Martin/Maarten.
I spent a couple weeks in Belize, and loved it. Great diving if that's your thing, plenty of bars/restaurants, good beaches, jungle/ruins tours, etc. We stayed at the far south end of Ambergris Caye, in the very last place available to tourists before it turns completely residential. We rode a bike everywhere and drank a ton of Belikin beer.
Mexico has some pretty nice places also. I've been to Cancun/Playa del Carmen a dozen times, as recently as two years ago, and always enjoyed it. Crime in Mexico has gotten really out of hand in the last few years, but is typically not rampant in the resort towns. I'm on the fence now whether I would go back, mainly because I don't want to give my travel dollars to a country that refuses to control its emigration, crime, and corruption problems.
There are lots of great places to go in the Caribbean, and you'll likely enjoy the Keys also. The only places I would highly recommend avoiding are Jamaica, St. Croix, and St. Thomas. Just way too much crime on those islands to ever let down your guard enough to have a good time unless you stay completely within the confines of the hotel, which isn't a vacation to me. I like seeing the sights, learning about the island, the people, and their food, etc., not just laying on the beach 24/7 and eating in hotel restaurants.