First off let me say that you will love the Conquest! A fine ship.
While in Jamaica try contacting Carolyn or Errol Barrett at http://www.Barrettadventures.com
They have a great tour operation and will keep you from all the pan handlers, beggers and drug dealers while you are in port. (I already have her book for the first week in Nov.)
They will email you a list of all their tours and prices.
We took the Hilton High Country Plantation tour last year and still talk about it. It also comes with a breakfast and Jamaican lunch! Very good food and great tour. Carolyn told us many stories of the people and the island and she is very informative. We topped it off with the Rockland Hummingbird tour, for an additional $10 you can actually have hummingbirds sit on your finger and drink from the tiny alcohol bottles you find on the arlines. Of course the bottles are filled with sugar water
There are also several other birds that will come up and eat seed from your hand! Also the view, Wow the view... MoBay from up there is breathless -- a total photo op!
In Cayens I would reccommend Captain Marvin's Sting Ray tour. Less expensive and less crowded (the group is anyway) than the ships' tours. His place is a few blocks to the left of the port where the tender drops you off, but well worth the short walk. They also have a web site. I am not sure but believe it is http://www.captainmarvins.com
In Cozumel I usually just do what ever. Being an active scuba diver and having been in Cozumel many, many times I have several places I go to...diving, restaurants, etc. If you have been to Cozumel in the past (several years back) you are in for a BIG surprise ...it is beginning to look more and more like Grand Caymen with all the upscale shops, etc.
Enjoy your trip!