Hi Dangler and MeetingMickey2006,
I am going this July, July 13 to 19. I've asked this same question and been on many July threads.
Here's the advice the good folks here have given for conquering summer. If at all possible (we will, we're morning people), be at the parks FIRST THING. You'll get a lot done in the first hour. Spend the morning in the park, then break. Have lunch, go back to resort, swim, NAP. Go back in the evening. You will miss the worst of the heat and crowds this way. Use Fastpass whenever possible. In MK, MGM, and Epcot, take advantage of the many indoor attractions and air-conditioned shops. This is less possible in AK, it's mostly outdoors and it seems 10 degrees hotter than other parks, is what folks are saying. Wear loose comfortable clothing, and a HAT. Wear loads of sunscreen. Drink loads of water. Water in the parks is $$$. Some options are to bring in your own bottled water -- if you don't want to lug it around you can rent a locker in the parks, store your softsided cooler there, and everytime you pass your locker, grab another bottle of water -- or you can fill up you water bottle with park water. However, many folks say the water in Fla. tastes bad. Some have solved this problem by buying special filtered water bottles.
Buy rain ponchos at the dollar store and take one into the park with you each day, then discard. It seems to be a better solution than buying one more expensive heavy poncho and having to lug it around after the rain is over.
I plan to wear Teva sandals, but if you plan to wear sneakers, have an extra pair for all, because after the shoes get wet they will be very uncomfortable.
If you plan to eat on site, make some priority seatings (PS) 90 days out, because the restaurants are busy at this time.
Dangler you don't say where you are from, but meetingmickey2006, I am sure the heat in Fla. won't be much worse than the heat in Oklahoma. Don't know how much humidity y'all have though. We have PLENTY here in the DC area.
Hope this helps!