if you are in san francisco you don't even have to be discreet. i used to always see people rolling up fat blunts at the McDonalds on Haight and Stanyan at the entrance to golden gate park. the only thing i'd worry about is people trying to steal your ganja.

but yeah you could probably get away with hitting a compliated-ass bong on the street in san francisco and nobody would glance twice at you . Oh how i miss that city sometimes.