My fiance and I are vegan.
Every day they serve a salad, soup, and 2 guisados (dishes) plus an extra (like rice), as well as a dessert, all for 50 pesos each. We ate there through for a whole week, and were very happy with the food. The food is not very fancy, but it's filling and very authentically mexican. Even my father who is not usually happy eating vegetarian, let alone vegan, enjoyed the food. They also were very understanding when we told them we didn't eat dairy nor eggs. Some desserts had local honey, which we eat.
Cons: Not too fancy.