Re: The point in september
I went to the first weekend last year, and was still really bad. Saturday was a lot worse the Friday... so if you want to ride a lot, plan on doing most of your riding on Friday night (and maybe getting a fastpass for Saturday).
Halloweekends is getting so popular, I think the days of seeing small crowds are over.
You may want to check and see when schools start in the area and go that weekend... I don't know if it will make any difference at all, but it may help a little!
Also, keep an eye on the weather... I've made trips to CP in September where the winds were really bad and TTD and other rides couldn't run a full schedule... there's also a big possibility of rain.