We've watched the parades from several locations throughout the years.
We love watching The Halloween parade right at the beginning of it in Frontierland (this was mentioned above). Not tons of people and as soon as it's done you can hit some rides with less lines, because so many people are still waiting for the parade to finish. You can also race your way to Main Street if you'd like to watch it again (which we have done).
Last year my DD21 and I watched the afternoon parade from the top of the train station - there was barely anyone up their with us, which was awesome. I did tell a few little kids they could stand in front of me by the railing so they could see better, but I don't count them as part of a crowd - their parents were close to us, but that was about it. I found it odd that practically nobody was up there. We loved this spot and we'll stand there again in March.
Have a great trip!!!