If the ships are there, you'll be fine.. Many ships are crossing at this time of year to the Caribbean from their summer in the Med. But any ship that is in the Caribbean will have an itinerary to make the most of the weather. Plus, ships can quite easily get out of the way of any storms. The Caribbean tends to be calm sailing all year round, with the exception of the occasional hurricane. But these are pretty much done by November.
I highly recommend WindStar Cruises, by the way! See why here: https://traveleater.wordpress.com/windstar-cruises/ over 6 years ago
I have cruised in Oct and Nov and the Caribbean was great. Florida was too cold in Dec though! St. Maarten was too chilly to swim in Dec but it was a wet overcast day, some people were swimming though. I would plan for between high 70s and mid 80s. over 6 years ago