The buffet was amazing, but like others have said, it could be tough for vegans to know what is vegan. It cost $99 pesos on weekends and $84 on weekdays. On the way out we saw the veggie burger cost $20 pesos. The place is huge and beautiful in an old colonial building humming with voices of happy patrons. They did have a jell-o type thing on the dessert tray. I'm not sure if that can be made veggie or if they just have no idea that jell-o is meat cube.
Note: the map shows it as being somewhere in the middle of nowhere suburbville. This location is actually right in the Centro, a couple blocks from the Zocalo.