CM is one of the most popular restaurants so it is fully booked most of the time. It's better to keep checking online daily to see if you can get a cancellation. You can continue checking even after you arrive at DW. Cancellations will come up because CM requires a credit card guarantee so people who change their plans will cancel to avoid the financial penalty. On the other hand, it also means anyone who doesn't cancel will show up for their reservation so it makes getting seated as a walk up harder. If nothing comes up you probably have the best chance walking up before opening or near closing.
