I would think it would be a shoulder season, between Memorial Day and the summer peak season. But what holds true here in Anaheim doesn't always hold true in WDW.
Hello! I am new here. Anyways, me and my wife always vacation at Disney in May. However, we go at the beginning of May. We never wait longer than 20 minutes for most rides. Everything I have read says from Memorial Day on is pretty busy. That is why we go at the beginning.
Last time my DH and I were in WDW in May was for our honeymoon in 2005. At that time we vowed never to go back due to the crowds and hot hot weather. We now stick to October and Feburary