If you're not going to DLRP at a busy time (I never have) then you can find a great spot on the route in Fantasyland anything up to 5 minutes before the parade is due to begin. We usually pick our spot up near the Bella Notte outside seating area, but on the opposite side of the parade route (there are benches there). Its very near the start of the parade, and apart from in Christmas and Halloween season, its also one of the 2 spots where the princesses get down off their float and dance in the parade.
Elaine