You should give a try two Costa Rica, there is to wonderfull hotels exclusive for adults, all inclusive and clothing optional, one up in the mountain close to many tours like volcanoes, rafting, waterfalls, coffee plantations http://hoteldesirecostarica.com and one on the beach close to national parks, zip line, atv's, rappeling, horseback riding http://www.copacabanadesirehotel.com you can combine your nights between both hotels and get more benefits.
Costa Rica has beautiful beaches, rain forest, national parks, waterfalls, volcanoes. Give it a try!!

Costa Rica sounds great...but I don't know if we're up for all the adventure the Desire brand offers.

Look at Turks & Caicos ( airport code PLS) Check out The Regent Palms Or The Somerset resort...both have what you are looking for, The Regent Palms has a world class spa, and both resorts have beautiful suites , great staffs and wonderful restaurants on site and nearby.

Costa Rica will not have the beaches or snorkeling that you are looking for. It's main draw is sightseeing.

Turks and Caicos' Grace Bay Beach is gorgeous, but snorkeling for that area is not great either. You'll need to go down to the Coral Gardens area or take a snorkeling tour. Even then, I didn't think the snorekling was that great. T & C is flat and scrubby. The exact opposite of PR and St. Lucia.

Curacao does not have long stretchs of sandy beachs. They have coves and inlets mainly on the West side. The sand is made up of crushed coral, so we felt water shoes were necessary. You will need a car and a good map to find them or take a beach hopping tour. The topogrpahy reminded me of Arizona with access to water. I did care for the snorkeling there either.

Mexico is one our favorite destinations and we go about once a year since 2000. The topography is lush and jungle like in some areas. The beaches are white sand and the water is clear. Not as much as T & C, but much better than say St. Lucia or Costa Rica. Tons of things to see and do off property; Mayan Ruins, cenotes, caves, jungle tours, eco parks, animal reserves, ATV, Zip lining, sailing, snorkeling.

5th Avenue in Playa del Carmen is blocks and blocks of pedstrian walkway with restaurants, bars, shopping and entertainment. Some of the best snorkeling can be found in Akumel where you can swim with the turtles and Yal-Ku lagoon. The best snorkeling we've found in that area was at the Ka'an Sian Biosphere. About 1 1/2 hours outside of Tulum. You need need to take a tour to get there.

From Playa del Carmen you can take the ferry over to Cozumel. Great Island for diving and snorkeling. San Miguel is a cute town with good inexpensive restaurants and tourist shopping. There are beach clubs, and Chanakaab Park is a great place to snorkel. From what you have described this area seems to fit all your marks.

Have you looked at the BVIs yet? Tortola might have what you are looking for with activities, beaches and dining. Plus you are a ferry ride from some other amazing islands like Virgin Gorda or Jost Van Dyke.

How about Roatan or one of the islands off Belize...namely Caye Caulker or Ambergris Caye?