I had the quickest time as Horde by starting at the Garrison, doing FFR -> Gorgrond -> Talador -> Spires -> SMV, Garrison Hearth -> Nagrand. I'd conjecture that the fastest path for Alliance would be SMV -> Spires -> Nagrand, Garrison Hearth -> Talador -> Gorgrond -> FFR, but I didn't get a chance to time paths Alliance-side. Like Jere said, both are relatively inefficient for leveling purposes, but this seems the fastest path to bang out that Menagerie daily. & of course, if you have the Mage Tower, all bets are off.
xoxo, Your Pet Battling BFF, Tamer Liopleurodon.