We were there last week and had ressies at MMs at 4:20 and the parade started at 4. We knew we would be cutting it close, so we stopped at MMs early in the day to see if we could move our ressies to 4:30 or 4:45 to be safe. They told us not to worry about it, we would be fine if we showed up a little late. That made me very nervous as I had heard stories about people being late for ressies and not being able to get in
but we kept it at 4:20 anyway. Well we watched the parade right by Star Tours and then once it was over, went right over to MMs and we were right on time. That being said, as long as you leave at least a half hour from parade start time, you should be fine (unless you decide to watch the parade from somewhere way away from your dining location, then give yourself a little more time).
Watching near Star Tours was a good location, although we had some very rude people around us trying to ruin it for us. We got there pretty late and still had a good spot. But had we been earlier, we could have had a great spot on the shady side of the street.