We go to Tony's every trip and we had the best chicken dish at San Angel.
I think it depends on which park you will be in and if you have kids. I honestly don't think that there is a single place that has "bad" food. I think some people make a bigger deal out of things.
I would go with Tonys. SAI is the only restaurant, in my life, that I have actually sent my food back to the kitchen and asked for something else. Even the second choice was not that great and I am a big Mexican food fan.