I believe it starts in Frontierland, but someone correct me if I am wrong. It takes a little bit to get to the castle and down Main Street, so I would say going by Towne Hall wouldn't be until 3:20-3:25? We were in the FP+ area and it was 3:15 one day before it passed the castle, and the next day I believe it might have been a little earlier. In my opinion, I think it's best to get near the front of the parade route, so you can be done with the parade before it gets to the castle and Main Street where most people are at. I personally like to have the castle in the backdrop of my pictures so I try to get in that area.