I haven't actually been there President's Day Weekend, but I've heard from a number of people, and I think it was also in the Unofficial Guide, that it's a busy weekend. If it were me, and I could easily change to the week before, then I would do so just to be safe...I hate crowds.
Hopefully, someone who has gone that weekend can tell you more about what crowd levels to expect. (I gave someone my Unofficial Guide to WDW 2006, so I can't look it up for you---sorry).