Personally, I love Jung Ma for my Empire characters (I also have characters on Sanctum of the Exalted, Republic faction - it was a deal with a new friend met through the forums) and another server or two.
So far there is a lot of random RP that I have found on Jung Ma, and whenever I interact in character with someone met while questing or exploring, it is well received (either they RP back at me, or they are just nice OOCly). For instance, just yesterday, I'd sent my companion on a crafting mission, then walked into a pile of mobs who almost got me. A Sith warrior who was running by stopped and saved me, out of the blue - I thanked him ICly, ran into him again a couple of minutes later, and we did several quests in character together after that. I asked him OOCly if he was normally into RP much, he said 'only occasionally', yet he was a great roleplayer while we quested. People are often quite willing to give it a shot if you roleplay "at them" gently.
But honestly, as long as you pick an RP (or RPPVP) server, I think you can't really choose wrong in this game, with this community. So far, I enjoy all the servers that I try.
P.S. If you're on Jung Ma, Empire side, feel free to say hi to my current mainly played toons, to RP with during quests and maybe get some story arcs going!
- Dev'eri'tess, level 24 bounty hunter, merc healer
- Neesa, level 12-ish Sith sorcerer
Or my jedi knight on Sanctum of the Exalted, if you are ever there (Olinore, Sentinel spec, level... 13-ish?).