I can't help you with experience, but since you are staying there it wouldn't hurt to go ask. Maybe go right at opening, and if they can't get you in they could give you a return time. Worth a shot, and not like you're going out of your way.
Walk ups are very rare there. My husband and I tried it a few weeks ago since we were staying in Bay Lake Tower for a few days and were turned away - they weren't taking walk ups.
Keep checking... constantly...like every hour on the hour....
Honestly I don't think that a walk up is a option there. We have had a 8:00 breakfast ADR and got there at 7:30 ish, and they were turning walk ups away.
Give it a try, nothing is impossible. You are staying right there you have nothing to lose. Get there 15 mins before it opens and hope for some pixie dust to fall your way. Good Luck. Keep us posted if you got in or not.