Play It Again, Sam - Hong Fat Noodle Company
Despite Allan's bizzare behaviour back at his apartment, Sharon comes along as his date, accompanied here by Linda as they arrive at the Hong Fat Noodle Company restaurant. (But you can just make out the edges of a temporarily applied plastic sheet on the window, suggesting that a fictitious name was affixed just for this scene).
Then ... CitySleuth could not find any record of a restaurant of this name in San Francisco. But as they enter, there are a few clues that helped him find this location. The girls climb two steps to the door, at bottom right there's a handrail and across the street is what could be a brightly lit nightclub.
... and Now, here's the same view from the restaurant today - note the similar, if not the same, handrail.
Then ... Inside, Allan continues making a fool of himself by demonstrating the right way to eat rice - by stuffing his face as fast as possible. Sharon has seen enough ... she ups and leaves. This shot yields another clue to the restaurant location - the sign across the road in the top right corner that reads 'Pepper'.
... and Now, there's now a takeout counter where their table was. So, enough already, where is this location? Read on ...
A search for 'Pepper' in the 1972 San Francisco street directory brought up the Peppermint Tree night club at 660 Broadway in North Beach at the edge of Chinatown. And across the street from it? The Yank Sing restaurant at 671 Broadway. This was where the restaurant scene was filmed (map).
As confirmation, a subsequent web search for Yank Sing yielded a 2005 online article about its history that mentioned that the restaurant was featured in Play It Again, Sam.
The location now ... In 1974 Yank Sing moved to another location in town where it is still in business. But its old location - the movie location - at 671 Broadway, now the VIP Coffee and Cakes Shop, looks just as it did, including those two steps and the handrail.
As it turns out, there was a restaurant called Hong Fat Noodle Company at 63 Mott Street in New York City's Chinatown (map), in business when Play It Again Sam was filmed but long since closed. It was a very popular dining spot with the local Chinese community and those fortunate others who knew about it (CitySleuth suspects Woody Allen was one of them and that he borrowed its name for the movie). Here's a recent photo of that location - the restaurant was upstairs via those stairs.