Current signup question is "Will you break the rules, be obnoxious or otherwise a negative presence on this site?" I'm open to suggestions for improvements :)
"Yeah, but only after the fifth pint" ... Access granted, but limited to /Perth?
(Here I am, writing this from Rockingham, WA, after a Friday afternoon in the city)
More seriously, I think that's fine, as long as there's no huge influx of people. Trolls won't tell you they will be disruptive, so moderation needs to happen in any case. The signup form is more a way to set expectations, I reckon.