Play It Again, Sam - Allan's Apartment, Exterior
Then ... Allan's place is in an alley just off of one of the City's steepest streets, so steep in fact that it has steps in place of sidewalks. Viewed from the alley, he is seen here crossing the street. The green corner building at the bottom of the hill is Vanessi's restaurant.
... and Now, This is the Kearny Street block (also seen earlier in the movie) between Vallejo and Broadway, in the North Beach neighborhood. (Its steps have been named the Peter Macchiarini Steps, in honor of a local artist). Vanessi's is no longer there, having closed down, as has the equally iconic Italian eatery Enrico's that used to be opposite, on the corner across Kearny.
... related trivia ... In 1968 Steve McQueen in the movie Bullit crossed over Broadway heading to Enrico's. The steep block seen above slopes up at far right.
Then ... Allan's closest friend, Dick (Tony Roberts), was waiting for him. They walk along the alley towards his apartment.
... and Now, this is Fresno Street and Allan's place is number 15, the red door on the right (map).
Then ... They chat outside 15 Fresno Street. But interestingly, when later on we go into his apartment we will find that the interiors were filmed not here, but elsewhere in town.
... and Now, it's the same door today as evidenced by the molding detail and the mailbox, but repainted.