Turns out a major scene was filmed around the corner from me in Long Island City, Queens. LIC is now home to dozens of film and TV shoots each year, but this is the earliest thing done here of which I'm aware. The below site is that of a pro location scout, and has amazing shots of the NYC area. He has a three-part post on locations for The Warriors. http://www.scoutingny.com/?p=6633
This was the original threatrical cut of the print. I guess the cultists don't much like the director's re-vamped version now available on home video.