Well don't go to Florida expecting it to be sunny and warm in Feb. Florida does see its fair share of cold temps. That being said pack warm clothes. Dress in layers because the days might be a bit warm like 60 degrees but once the sun goes down so do the temps. The temps could be as colds as 40.
We have gone many many many times in Feb and we always pack a coat with strechy gloves and a hat. Two years ago it was so cold that the sprinklers that come on during the night had turn things into ice sculptures.
Oh as far as crowds it will be very crowded that week because a lot of schools have winter break, its the week of the Daytona 500 race and a lot of race fans go to Disney. There is also a twill mania competion that is held every year during Presidents week. The yearly cochelear impant convention occurs during this week. So use the fast pass options for the popular things.