I was born in Altrincham and I lived all over south Manchester at various times. One side of my family (Cheadle, Gatley, Stockport area) were City fans but not match-goers, the other side (Altrincham, Sale, Stretford, Urmston, Davyhulme) were and still are fanatical Reds with season tickets even back in the day.
At one point in the early eighties, I was a student and lived in Rusholme and I could literally see Maine Road stadium from my house, and I used to take the bus to Old Trafford, usually with my girlfriend. The route took us through Moss Side (supposed City area at the time and with a rough reputation) and I never hid my red, white, and black scarf. We were sitting ducks, you'd think. But not a soul ever bothered us. In the early eighties. To me, that says it all.
Oh, I knew a couple from Rochdale who were City fans. And that's about it. Obviously, things will have changed, but judging by many of the comments here, Manchester's still red.