generally in the clubs i go to here in the states, specifically texas, the dress code is really lax. i have never seen someone turned down trying to get in based on what they were wearing
but again, most people know to show up to a club looking somewhat decent.
also, i have never been searched or frisked or whatev when going to a dubstep show,
only been searched on the occasional visits to the raves, and that was only ONE time (been to about 5 so far)
police are usually no where to be found, or there will be one sitting at the bar for half the show, realize nothing is going to happen, and go home.
generally shows are 18+, some 21+, i have even seen some all ages events or shows that were 16+ or 17+