March is when it starts to warm up and it does so quite quick. It's still dry so humidity isn't normally an issue. Temps should be in the high 70's and low 80's during the day. High 60's at night. Still a little cool for the FL people to swim but fine for everyone else. Shorts & tees but I'd bring at least one pair of longer pants and a sweat jacket/shirt for night time.
We have had cold snaps in March but they are not typical and usually only last about a day. Since you are looking at close the second week of March, you should be on the warmer side.