I watched that one, i think thats in the tenderloin district. no doubt there are many different meth users from all walks of life as there are with all drugs.Also, i think that with san francisco you have quite a big meth culture anyway which sort of permeates throughout the community, its quite popular amongst the gay community in many areas which if you look at san francisco probably means its in plentiful supply. There was another documentary in chicago about meth and it was mostly focused in the boys town which is considered a gay district other than that i think the use is quite obscure in that city. I think meths customer base varies drastically from region to region.

heres the link to that documentary. Its shit quality but clear enough.
http://www.youtube.com/watch?v=6Wa2tPrZzks

This is another study i posted a while back about drug abuse amongst gang members, particularly meth and crack.
http://www.gangsterbb.net/threads/ubbthreads.php?ubb=showflat&Number=710053