WYSIWYG is right on ! The equation is simple. You won't affend anyone by not boozing, but you almost certainly will offend some of the crowd if you do. If you get dry throat like I do ( even when it's just some new people in the kitchen ), water is best. AND, if I had actually paid to attend, I would have felt slighted by the arrogance and rudeness of the performers.

A trick - if you play a pub and you think the mood and the crowd and the client warrant a bit of "let's get things going", tell the bartend prior to the gig that you want ginger ale in the glass or water in the beer bottle and that it's "our little secret", even when someone in the crowd buys the band a round.

gnu