I've been three times to the San Angel Inn. The food is delicious - dessert in particular (Isla flottante = top 5 desserts of all time). The building and decor are beautiful. The service impectable. Cons: somewhat crowded, and you are going to leave with a *serious* dent in your wallet. Do ask the gentleman at the coat check for the little history 1-sheeter to learn about the history of the building as it is very interesting.
The real interest is the people-watching experience for me. I am a middle-class Canadian, and like most American & Canadians, we're used to everyone looking basically the same. For the most part, you cannot pick out the average person on the street and "see" their economic level. Now, at the San Angel Inn, you get to see upper class splendor in full display: grand dames surrounded by their meticuously over-groomed broods. Siblings in matching outfits - perfectly arranged - playing with their nurse-nannies in the garden, appearing to have decended from the 1950 by time machine. One table next to you might appear to have sprung from a telenovella, while another seems to have strolled in from a Great Gatsby remake. It's quite the sight for the likes of me, in my frumpy egalitarian northern wardrobe, to be sitting next to people who probably paid more for their outlandish shoes that I would for my entire 5-year footwear budget.
So, go for the food, and enjoy the side show as a benefit. And get that Isla flottante for dessert!
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.