*** has quite a number of reviews of SF providers (remember that *** originated in Cali). Also, if you are into the AMP scene, they are literally everywhere. And if you are into the strip club scene, many girls in the clubs will negotiate for additional services (beware of rip offs if the girl seems too pushy). The higher end clubs (i.e. Mitchell Bros., Century Theater) has better looking girls, but of course it will cost you more. Some of the porn stars that headline in the clubs, for the right price, will meet up with "fans" in the dressing room.
You are correct that it is a hobbiest playground. Basically, the police look the other way (they feel there are more serious crime to deal with). The only thing they will not tolerate is the streetwalkers.