My wife and I went to Walt Disney World in July of 1999. Agree with Mouseteacher that it was hot and humid, though not as bad as I expected.
Though, I wore a backpack much of the week and my back became really chaffed from the sweating and rubbing.
I also had bug bites on my legs, which I put toothpaste on to stop the itching. It worked and I was minty fresh.
I didn't think the crowds were that bad for summer either. At
Disneyland, our usual theme park destination, summer crowds are to be avoided. Maybe because there is just so much more room for everyone at WDW that it wasn't much of a problem.
We must have had a pretty good time in July since we will be back at WDW this July, staying at the Wilderness Lodge. We're looking forward to it - heat, humidity, possible crowds and all.
I'm sure you'll have a great time on your July 2004 vacation!
Matt