[Mr Downtown]

Not Pasadena. No house numbers that high in the business district.

Keyes Mercedes is (or was) at 5746 Van Nuys Blvd. The sun angle would be right (west-facing façade just after noon in winter). Different building today, though. And Mercedes, in a serious Spanish Colonial building seems a little odd out in the Valley in the 20s.

My guess is 5746 Sunset Blvd., later site of the KTTV station and now a new school, based on the simple fact that no streetcar tracks are visible. As that's on the south side of the street, the photo would be late summer afternoon, chosen so as to have sun on the façade.