I was able to go to the one in September. It wasn't so much that the parks were crowded. It was the lines for the pictures with the characters. We spent an hour each for Darkwing Duck and Chicken Little. We didn't even bother with the Rescuers line. By that time, half the night was over. Yes, there are a lot of passholders when the events are condensed into three month spans.
I don't know how many locals were there, but you do get to meet and talk to some really nice people waiting in line. All in all, I enjoyed it. I would just use a different strategy next time.