August is not bad.  
  
If you go on the weekdays of August you won't have to worry about crowds too much. July is the worst of the three months, June---July--August, in my experience. 
  
I'd recommend you go sometime in the middle of /late  August.  Sometime around there. Just avoid Saturdays. Sundays aren't bad.  
  
Don't waste your money on a flash pass, like other people tell you to.  You can get re-rides on Tatsu, Deja Vu, and Terminator in the morning if you wish by going with those three as your first rides for the day. You can easily get re-rides on the rest of the rides there any time of the day, excluding X2.  
  
I usually save X2 for last and if there's time left over (there always is) I may fit in a second ride of it or additional re-rides of the other rides. But I don't care for re-rides on X2 personally, so I go ride Goliath again hehe.