Sarahbelle you will be fine with the heat in Florida. You get the hot humid weather in Kentucky too. The only problem in Florida is the sun is hotter. What really gets people is excessive exposure to the sun and dehydration. It can creep up on you easily. Even well conditioned folks can be susceptible if not careful.
I think compared to WDW Universal has well thought out ride lines to help with inside outside waiting.
Wear plenty of sun screen.
Drink plenty of water.
As noted above have lunch in a nice sit down air conditioned resturant. Hint: Mythos is lovely in IOA.
As snoopboop noted above take strolls through shops for a quick cool off.
If you stay onsite hit the park with your early admission then take a break for a cooling snooze in your room or head to the pool and then back to the parks later.
I would recommend costing out the savings of staying onsite verses not. If you stay at RPR, HRH or PBH you will get early admission as a onsite guest and Express Pass for everyone. I have been to the parks in the summer and there is no way I would do them without EP.
Will add to phillymummer list
Beetle Juice is outside and is shaded.
Mummy inside
Simpsons inside outside
Transformers inside
Animal actors on location outside shaded
Flight of Hippogriff outside
Dueling Dragons outside
Depending on line Hogwarts express inside outside nicely air conditioned inside.
Jurassic Park river adventure outside shaded
Terminater inside show
Horror make up show inside
Have a great time