WoS would be good since (I believe) it's a hot zone right now. If you can't find a group there, I'd take him to PoV until he hits 62, and then BoT until 65-66. At this point, try again in WoS or MPG. Definitly MPG at 66-69, then RSS until 71-72.
There's really no real PLing even after 65 IMO. I'd try to group him from 65+ in those zones listed. Also, try Burning Steppes, Direwind, Icefall, and eventually Valdeholm. Maybe even try to get some guildie friends or in game friends to let you keep him in group for XP while you help with buffs and heals from out of group with your other boxes. I know I'm always willing to help someone get XP on a lower alt as long as they're helping from out of group with their main(s).
Anyway, just my 2cp, I'm sure others might have more of an insight.