Margaret,
Being from the Bay area, I too do most of my diving in Monterey, and if you are used to these waters, then I dont think youll have a problem diving in Florida with a 3mm suit.
When we went to the Keys last year, the water temperature was in the low to mid seventies and we were very comfortable diving in a 3mm shortie, but then again, we dont tend to get cold that easy.
Also, a shortie will not protect your arms and legs if you happen to rub against a fire coral for example. (Another lesson learn the hard way) but other than that, I still prefer a shortie over a full suit for warm water diving.
Have a great trip.
Triton