The parade route runs from IASW up in Fantasyland, down through FL, enters the hub and stays to the East side (it doesn't circle around in front of the castle like WDW's does), and then goes down MS, and exits out of Town Square (on days when there are 2 parades, it can return back up MS and do the opposite - at least it used to do that in days gone by).
TS is a great place to view the parade - especially if you can get the benches up on the train station platform, or curbside seating. All along MS there you'll have great viewing, and then there is a section in the FL esplanade approaching IASW that has some slightly elevated platforms for parade viewing (originally added for that mess they tried to force on DL years ago...Light Tragic -er Magic. Sorry - I hated that thing).
I'm sure locals will chime in with when to stake out a spot...it really depends on crowd levels and when in Sep. you'll be there. DW and I are native CA'ians, and I am a former CM, and have years of experience with DL as an AP holder, but I simply don't get there as often anymore (3-5x/yr vs. multiple x's/month like many of the locals do). The visitor dynamic seemed to have changed with the 50th, and has remained stronger since then, even through traditionally less crowded or off-peak times).
Good luck in your planning.