There have certainly been people who just walk up and are able to be seated, especially at slower times of the year. I'd NEVER count on this happening, though ---- just saying it's possible. I've walked up on the spur of the moment, in a quiet season, and not gotten in. If you can't get a reservation, don't stop trying. Some people have reported success 2 days before, so keep trying once you get to Disney. Good luck!