I would go if I were you!
Yes it is hot and crowded, it is peak season. Keep in mind the LA heat is a dryer heat than Florida, not normally very humid.
I think
www.mouseplanet.com may have a link to weather.
Yes, DL has fastpass too. 2 rides that have fastpass you won't find at WDW (Indiana Jones and Roger Rabbit Car Toon Spin).
I would approach it as you would if you were going to WDW in July. Make a good plan, allow youself plenty of time to see what you want to see. DL is much smaller than the MK so there is less walking. If you have limited time, make sure you focus on the attractions that WDW doesn't have (Matterhorn, Indiana Jones, Roger Rabbit, Mr. Toad) and the attractions that are better at DL (my opinion only

: Pirates, Small World, Haunted Mansion).
Make sure you visit the Disney Gallery above Pirates and the recreation of Walt Disney's office which is housed in the Great Moments with Mr. Lincoln building.
Are you going to go to California Adventure too? Lots to think about, if you have more questions fire away!
