This decent vegetarian restaurant has a few tables inside, and a handful outside. As far as I know, it is the only vegetarian restaurant near the Zocalo. I ate lunch outside on the nice, quiet street. I didn’t get bothered by any hagglers even though I was a woman eating alone…mostly just businessmen walking by.
The menu included juices, salads, breakfast, egg dishes, and dessert. I had an emparedado de aguacate (avocado sandwich with tomato, lettuce, and onion). It came with french fries and was 37 pesos (~$3.70). The bread, as it tends to be in Mexico, was tasteless and dry. For dessert, it was coconut ice recommended by the waiter.
Overall, the lunch portions were smallish and the food was above average. If you can go to just one vegetarian restaurant in Mexico City, make it Restaurant Yug, which is awesome! But if you’re in the neighborhood and want some basic vegetarian fare, hit up El Vegetariano.