in between liberty square and frontierland theres a bit on your map marked as the shooting gallery, outside this theres a couple of old chests that are a lovely place to sit and have a drink or snack and mark your spot nice and early, then as it crowds out you can move forward a bit.
other places I've found are right at the beginning and end of the route and if you can get a pavement seat along main street. also above the station is a great spot to look down on it but you have to be there well early!
Basically if you're going at an busy time be prepared to mark out your spot well in advance (some people go over an hour ahead!) just look on it as time you can take to take in turns at restrooms, snacks, ice creams, drinks and to recap and plan the rest of the day.