Perhaps there is something out there I am missing but I would like to see people list adult stores, strip clubs with private booths, adult theaters etc in their area where it is safe to hang out, enjoy adult entertainment and masturbate.
I live in the Los Angeles area and as far as I know they monitor booths in adult video places here quite strictly so those are usually out. I know of only one place where you can enjoy yourself in public without too much worry and that is Studs Theatre www.studstheatre.com
It is pretty much 100% bi & gay men in attendance. They show gay porn on one big screen and then 1 small screen then straight porn and transgender porn on 2 small screens. You can feel free to wank it there and you will often find someone to join you. When I am feeling the exhibitionist I like to head over there and masturbate. I like to play it safe so I turn down those who want to suck me off (and there seems to be no shortage of willing participants), but there have been a couple of guys there that have stroked me off. The only draw back is that it can get crowded and then you can get some oddballs and it can be a bit gnarley. The best time to go to not be as bothered that I have seen is during the day. For couples I have seen couples in there a couple of times around peak times and they attract a crowd immediately. So if you like an audience you will get one.