Originally posted by Tetsu
Avoid weekends. That goes for any park.
Nope. I've found Sundays and even sometimes Saturdays to be the best times to hit Valleyfair. Especially during off-Summer months. Mt. Olympus does generally the same between weekends and weekdays. BGA was honestly not horrible any of the times I've been there, all of them landing around Saturday.
So that is an easy generalization to make...however, again, one that isn't true [;)]