The Kitchen at the Hard Rock Hotel. Not City Walk and it is pricey of course, but it is honestly the best breakfast buffet I know of. Also you can use your AP discount so that helps a tad.
Just caution though, the tip automatically added on can be a bit outrageous, and I am a generous tipper.
Just caution though, the tip automatically added on can be a bit outrageous, and I am a generous tipper.