Great post at PPR. The way I see it, if you have to ask if you can take their photo you don’t will not get able to capture the natural occurrence of the street. I’ve done it several times while I lived in L.A. but then had to stop since several of the locals at the area have warned me that I will get mug for sure if several of the degenerate see me carrying a camera. LOL.
If you're borrowing inspiration from any copyrighted material, even if it seems clear to you that your use is transformational, you're in danger. If your use is commercial and/or potentially objectionable, seek permission (though there's no guarantee it'll be granted) or be prepared to defend yourself in court.