The least crowded viewing location is almost always Frontierland, where the parade route starts. PP is right that you don't have to be right on the rope line or front row to see the floats, and your best chance to get closer is in Frontierland, not on Main Street or the hub, where everyone seems to think they have to watch the parades from. I would think you could get a decent spot 20 minutes or so before the parade if you watch from Frontierland. This is all assuming that you aren't going at a super crowded, peak time.