Since Veracruz has very few vegan/veg options, I checked this place down after a recommendation from the owner of the now closed "Olivo." Some key points: it's in Boca del Rio, a 15 minute or so taxi-ride from central Veracruz. It's also in a retro-esque shopping mall, taxi drivers won't know which side but it's easy to find once you're there.
Each time I went, the place was packed with locals and you had to sign a list outside indicating how many in your party and whether you were willing to sit with others.
The food itself is pure greasy-spoon vegetarian indulgence. Many plates contain cheese or cream, but every time there was more than enough to satisfy a vegan - great pozole, veggie chorizo, steamed greens, etc. The place has been open for more than 20 years and has a unique feel. Worth seeking out for a big buffet (keeping in mind that they close by 6 p.m.).
Cons: not very vegan, out of the way