Yes there are restaurants in Mexico, San Angel Inn (the TS place) and Cantina San Angel (CS place).
We have eaten in the San Angel Inn and loved it. The atmosphere is fabulous and very romantic. There is a little boat ride in the pavillion and the restaurant sits on the river, it is lit like you are outside at dusk on the mexican river.......so cool!!
The food is very good, but as PP said, it is not Tex Mex and more traditional than Americans are used to, so check out the menu online before you go. Make sure there is something you like.
I highly recommend it for a nice, romantic evening dinner.