My mother and I went in July of 2000. It is worth doing, but it is hot and muggy, and it is defiantly more crowed than any other season.
We went to the parks first thing in the morning and stayed until about 1 or 2 PM. Then we went back to the hotel for a nap or swim. We had dinner at either the hotel or EPCOT and then did our evening thing. This kept us out of the parks at the hottest and busiest part of the day, and gave us a much needed break.
Use fast pass as much as possible, it will save you hours! And try to alternate outdoor rides with indoor rides, it gives you a break from the sun and heat.
Get to the water parks first thing, do not wait until later in the morning or afternoon, you may not get in.
Have a plan of attack for the parks, the better organized you are, the more you'll get out of it.
Well, I hope you have fun, good luck!
Chicago526
1984 Contemporary
1998 Ft. Wilderness Cabins
2000 Port Orleans F.Q.
2003 Ft. Wilderness Villas