[I went there on March 2015, and the prices were NOT the same as indicated: 34Bs. the set menu. The restaurant is now all vegan and the hours were as follows: Monday-Saturday 12:00-14:00]
Even if the menu may seem a bit expensive (34Bs.) it is worth the money, for this includes a salad (from the salad buffet), a soup, a main course, a drink, a mate and bread.
The day I went I had the salad (you can freely chose from many options: lettuce, onions, carrots, potatoes, etc.), the 'sopa de papalisas' (aka ollucos, a kind of root crop similar to the potato), the 'pastel de garbanzos con arroz' (chickpeas pastel with rice), an amaranth drink and an anise mate. The other option available for the main course was the 'empanada con verduras' which was really good.
The service was very friendly, allowed us to have a free refill of the drinks, to go back for more salad, and so on.
Small indications: the restaurant is situated in the 2nd floor so you have to take the stairways, and then you have to pay first at the entrance and then remit your tickets when you want to have your soup or your main course.
I only wish they had a smaller menu for a cheaper price in case you're not that hungry and you don't want to spend 34Bs.
Cons: Price (but still fair)