Over the years (I grew up in Winter Park.), I've visited the parks many times during July. Even now that I no longer live in Florida, I often go back during the summer months to visit friends and family...and WDW, of course. If July is the best time for you to visit the Mouse, then GO! But go prepared. It will be hot and humid, and it will rain every afternoon at precisely the same time (or at least it seems like it). However, the generally short downpour can really work in your favor. Many of the theme parks, but especially the water parks, will empty-out during the deluge. As far as the temperature goes, take breaks during the worst of the afternoon heat. Also, those misting fans can be a real lifesaver.