Take a look at this thread for a list of guilds and community events: WrA Information & Directories (Guilds | Communities | Events) - #149 by Rudaba-wyrmrest-accord
I’m not sure exactly where you’re looking but the Horde RP community is one of the most active and engaging on this game, and probably one of the last.
Orgrimmar is your best bet for random walk up RP but there are a lot of guilds and events that happen elsewhere.
Good luck!