What band is it? If they are mostly instrumental, it could sound pretty good up there. If they are a pretty heavy band (loud) and their fans are a bit rough, then it might be a tough situation to record in.
I'm used to hanging out with friends pre-show and then finding my spot about 10-20 minutes before the band hits the stage. They are used to it to. At first they thought it was wierd I didn't want to hang with them, but after I started giving them copies of the show, they changed their minds!