Judging from appearances, I'd say this is from the late 80s, but no way to be certain. (I invite all deadhead-readers to jump in with chronological estimates.) Bobby is wearing some extremely dorky short-shorts. The late Brent Mydland is on keyboards, which means this performance was recorded before July 1990.
I don't know where this concert venue is, but the crowd is ENORMOUS!
Grateful Dead - Let the Good Times Roll