Late fall and early winter are the best times. Kids are in school (except for the holidays), weather is warm and the ships sail full so yes people cruise during these times..
2008-Valor and Glory
2009-Spirit and Splendor
2010-Freedom of the Seas and Mariner of the Seas
2012-Allure of the Seas and Navigator of the Seas
Yes. We went in early December last year. The weather was cooler for shopping and land based tours but we found the water in Grand Cayman too chilly for swimming. The said that the water was unusually cool and is usually fine that time of year. The water was much better in Cozumel.
We have friends that do the Rock Cruise in late January. They usually dive for their excursions.
We've done Valor in October 2006 and Liberty in November 2008. I'm from central Canada, it gets pretty hot here in summer, but I hate extreme heat. I figured this was the best time for us to cruise. Turns out I was right. Never wore a jacket once, except our last night Orlando after the November cruise. They almost had frost that night!
Plus, the sales seem better this time of the year IMHO. At least it has been for us.
I cruised in early Feb on the Inspiration and loved it. In Buffalo, it's like 5 degrees that time of year. On the cruise, weather was in the 80s. Water in Grand Cayman and Cozumel were perfect; I spent both days at those ports in the water the whole time. PLUS, hurricane season is gone by then so no worries about last minute change of plans.
Carnival Inspiraton, Feb 2006
Carnival Glory, Aug 2007
Carnival Liberty, Aug 2009
When I was living in NH I cruised mostly in February or March to thaw out.
“Twenty years from now you will be more disappointed by the things that you didn’t do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover.“
If you are going on a Western caribbean cruise, the colder months are the best, as the weather there is in the 80's instead of the 100's like in June, July and August.
The Eastern Caribbean island and southern Caribbean are also fine, as they are out in the warm ocean water, so thir tempertures don't change much at any time during the year.
The two you have to be careful of is Bahamas cruises and Bermuda cruises in January, February, as they are both decently north (in the Atlantic, NOT Caribbean) so they can get tempertures regulary in the low 70's or less and obviously the ocean gets too cold to swim comfortably in.
(remember Nassau is straight over from Orlando and Nassau is striaght over for South Carolina)
Many days will be comfortably warm in those months, but it can be hit or miss, especially if you enjoy swimming in the ocean.