Tried it last October, and really enjoyed the food. We had a really bad table location, right next to the servers station. I would agree that there aren't many great spots, other than the waterside tables. Having said that, it didn't really diminish my experience, I always seem to end up in the less desirable spots!
I'm not an expert on Mexican food, I'm only used to the Americanized version. We all had a great meal. I was happy with the kids menu, in that DS7 tried something new. He really liked his Quesadilla de Pollo. He also ate most of my appetizer, (Crema de Elote - Corn chowder with cheese and diced poblano peppers) which was not fair, as it was really yummy. We would probably eat there again, though with all the choices at Epcot it may be awhile before we get round to it! The service was really quick, I have seen people say that it's very slow and not very good, but we did not experience that at all.