We went the first week of May in '03 and the last week of May in '05. We really enjoyed both even with Mem. Day Weekend last year. The first week wasn't nearly as crowded as the last, but the hours were shorter. We found we liked the extended hours much better and the crowds just weren't THAT bad. It happened to be hotter for us during our earlier trip but it's not usually so bad. We love May and will go again during that time!