I would much much rather do the Belize/Roatan route than Jamaica Cozumel. If you go google Victor Bodden for Roatan. He is very inexpensive and will show you everything on the beautiful island for about $35 pp. You just pay for anything extra. For $5 extra you can go to his house and see animals, including monkeys you can get into the cage with them and they jump around on you.
I just did this route and so did Zydecocruiser, so Im sure he too will have a lot of feedback. He put up a link to his pictures recently. We got back early December. (though I try to go every year for the last 4 or 5 years to Roatan as it is my favorite port)
Belize you can get any drugs you want at the port. Its the only port I know of that you can even buy pain meds. I was surprised. I had bought so much stuff in Roatan, a beautiful mahogany bowl and some Lenca pottery and on and on, roasted chocolate beans, you name it .. that I did not buy as much in Belize as I might have.
Carnival has a free beach near their new port if you want a beach day in Roatan, but I think this of all ports is really worth getting out and seeing the sights.
Both ports are known for their diving and the crystal clear waters.
Conquest 7/21/13, Miracle ALASKA 8/27/13, Miracle HAWAII 9/17/13, Celebrity Summit, 11/30/13, Celebrity Summit, 12/7/13, Celebrity Constellation, 2/7/14, NCL Epic 3/2/14, Allure 5/4/14, Allure 11/2/14, Quantum 12/8/14