You can buy the Tostido chips and jar salsa right outside the restaurant (or in your local grocery store)

. Definitely not authentic.

I live in Texas where we have tons of Mexican restaurants on every corner: the chain Mexican restaurants, Tex Mex restaurants, and authentic mom and pop places owned by local immigrants. They do each taste different and we eat at all three types of restaurants frequently. San Angel Inn is not even close to any of them. The last time we ate there our food came out cold, not warm, but cold. Service is extremely slow and tables are so close you can hear every conversation around you. The scene is very pretty and peaceful though.