After 12/18 the resorts start to get crowded. As long as you are not there during the busiest week from Christmas to New Year you should be OK for a walk up with a short wait. Or make an ADR the day before you want breakfast there and you don't have to wait at all.
Most people just grab something quick at Rix or have breakfast in the Pepper Market. Not many take the time for a leisurely breakfast, but it's a great way to avoid the really early morning crowds for the buses if you don't mind getting to the parks later.