Yeah, if it's a glamorous movie, I doubt they are going to put trash on their sets.
OP, you should check some of the photographers in different eras who portrayed things the way things really were and not how they would be seen in a movie or a magazine. Check out Jacob Riis' "How the other half lives." I know it's not from the time period you're asking about, but his project was meant to shed light on how people were living in NYC outside of the public eye.
http://tjbogar.wordpress.com/2012/10...-street-arabs/
You could also look for photos of the Bowery in the 1950's. I'm sure those are not glamorous, as the area was also known as Skid Row.
One last point -- New York in the 1950's was in the midst of the post-war boom, which might account for some of the glamorous scenes you are seeing from around that time.