Good question, I'm sure one of our Hamburg residents will give a better answer.
From my (limited) experience on matchdays, both sets of fans seem to wander up and down fairly happily. The Reeperbahn didn't seem especially 'football' (for obvious reasons) however, there are loads of football bars on the sidestreets around the ground, near the fanladen etc (my geography is still a bit sketchy). This area is definitely a football area and all the bars are pretty welcoming. Both times I've been, the sun was out and the atmosphere on the streets around the Millerntor was great.
The first time I went, I remember asking in the club shop for directions to the Jolly Roger

I'm pretty sure it was Inga (one of the stars of the new St Pauli film) who patiently explained how to get there
