I would say slim to none for walkup unless you happen to get really lucky. We were there the last week of August this year, and there had to be at least 20-25 people just sitting and standing around outside waiting. I asked the CM if that was the wait for reservations and he said "Don't worry, you'll get in in a few minutes. All of those people don't have reservations and are hoping that something opens up for them at some point." That being said, there were plenty of open tables the entire time we had dinner. I'm guessing a bunch of ADR no-shows.