There are a couple of bands that I would love to have the chance to see. They're broken up but I'd love to see/hang with them afterwards. They are as follows:
A Global Threat - They are a street punk band originally from Maine but centered in Boston. They play pretty hard, fast and [towards the end] very well. I've seen them live twice before but when I was really most into them they posted on their Myspace that they had broken up. The singer, Bryan Lothian, is a personal hero of mine and the music he's currently making on his own is very good, in addition he donates almost all the money from his new music project to charities around Boston. I'd love to see them play one more time and hang out for a few beers afterwards.
At the Drive-In - So once upon a time the main members of the bands Sparta and the Mars Volta were part of the same band called At the Drive-In. They're in my top 5 bands of all time and their album Relationship of Command is my all time favorite album. Needless to say the singer and lead guitarist (Cedric and Omar of the Mars Volta) are insane live performers and I'd absolutely jump at the opportunity to see them performing some of my favorites live. As for hanging out with them afterwards, I think it could be cool. Back in the early 2000s the band did a lot of heroin but come the break-up they were clean. All-in-all I'd pretty much piss myself given this opportunity.
If it has to be someone who is still recording and performing?
Hands down: Chali 2na. My all time favorite rapper, former member of Jurassic 5, one of my favorite hip-hop groups. He seems like an incredible individual and the chance to see him live and chill with him afterwards would definitely be something. Seeing J5 before they broke up would have also been good enough for me.
Honorable mention to Blackalicious and The Krum Bums.