We were just there a couple of weeks ago. It REALLY depends on your personal body thermostat. Personally, I wear shorts at home on days when my DH is in his heavy winter coat.
We felt most comfortable with fleece jackets in the morning and evening, and could go either way between shorts and long pants during the day. (It was warm enough for shorts, but not so hot that you'd feel too warm in long pants.) We did swim in the heated pools, but needed to wrap up in towels after getting out of the water.
My DS and I spent one day at Islands of Adventure (with lots of watery rides), and were among the few people there wearing shorts. So we were walking around in wet shorts, while others were in wet jeans. Personally, I'd MUCH rather be in wet shorts, even if it is a little cool out.