I've eaten here a few times. It's OK. Something always seems lacking in the food and service. The food is Americanized Mexican with some authentic dishes thrown in like menudo and pozole.
I like the food at Viva Mercado's, but it's nothing special, and the service is lackluster as well. The sopa de fideos is pretty bland, as are the refried beans, rice, etc
All in all, Viva Mercado's might rate 4 stars, not because of the great quality, but because so much of the competition is so bad.