I'm in the same boat, flying in with my son. Consider Hammer's Lot on Abbott across from the stadium. That's where many TBD'ers go and Pinto Kenny hangs there also. People are friendly.
At the home opener tailgate, TBD folks are in the front corner of the lot, along Abbott (opposite the RV lot). Not sure if they congregate there for non-opener games. If any regulars can chime in about that it would be appreciated.
Edit: Check out the other Packers-Bills tailgate thread started by Hammered A Lot. More details there.