I went to San Angel in September and I have to admit I was a bit scared based on reviews I had read but it ended up being one of my FAVORITE meals on my trip. I believe this is what I got:
Filete Motuleno - Grilled beef tenderloin over black beans and melted cheese, ranchero sauce, poblano pepper strips and fried plaintain.
I am not normally a steak person, I find that it's always tough and chewy. But the steak at San Angel was WONDERFUL, it practically melted in my mouth. The menu is definitely more authentic Mexican food and not Tex-Mex which I think most of us are used to when we think "Mexican". I absolutely think you should give it a go, btw desserts are wonderful too I had the bread pudding and it was fabulous!