Trying to start to plan/put together ideas for things to bring for late November early December. I know nights can get chilly but how chilly. We r from Chicago do December chilly is 20 degrees at least ! If it's sunny it's a bonus and maybe 25 .
Although the temperatures can swing higher and lower I would plan on layers.
We love December. Sometimes it's warm enough to swim (80's) sometimes it can be cool (30's-40's). Generally you will need a light jacket/sweater in the early morning/evening and shed it during the day. Layers as @PrincipalTinker said are your best bet.
We will be there then as well! I was there the same week for a conference several years ago. First two days of the trip had highs in the 60s. Then a heat wave came and it was high if 90 the rest!
When we went the week before Christmas, it was 70s-80s. February was what I would consider bitterly cold for Fla., 40s and damp with a decent wind. It's difficult to predict.
Funny, this February we went swimming every day . Temps were in the 70s and 80s!
You won't know until you see the weather forecast close to your trip. I'd expect you'll need a jacket at night, but as folks have noted temperatures could be in the low 40s or in the 80s.