Like a lot of AP holders I plan on being there Sunday, the 15th. I upgraded my So Cal. Select in June (so I could go for "Free" on my birthday-I know, Disney Math
) so now I can go on Sundays, which I love.
Probably won't stay for the nighttime activities, plan on going back to see during the week. Going to get there early (pretend we are on vacation) grab FP and then leave when it gets crowded.
June is usually nicer weather. If you can go when the local APs aren't a factor, that's the time I would pick. I was there on the 2nd to the last day of the So Cal AP and it was crazy crowded!
Like PP have said, it'll be hot in Aug. but nothing compared to WDW! It's a dry heat
(usually) Get there early, use FP. DL can get crazy crowded. I've been to WDW in Jan, April, June, Sept, and Dec. and have experienced nothing like the grid lock at DL after the FWs are over.
Have fun no matter when you go.
Read all the hints you can. (Like eating at Whitewater Snacks at GC for a nice break in the day).