It's probably going to be faster to level as Arms (my choice) or Fury until Outland (or possibly BRD if you like to run instances), even with the recent buffing of the Protection tree. You won't get a lot of Protection's fun new toys until high levels anyway, and increased Threat when tanking (formerly the big reason to spec into Protection at a low level) is no longer a very big issue as you're leveling up.
That being said, if you really want to level as Protection, here are a few possibilities:
Prot + Cruelty/AttT Deep Protection And finally, if you decide to leveling as Arms or Fury, here is a sample build:
Arms All builds listed are level 50, and are leveling builds. I don't know the theorycraft 110%, but I'd tend to recommend picking up Cruelty immediately (first 5 talent points) and then going from there. If going Prot, I tend to pick up +dmg talents when possible, then fill in with some avoidance talents if I need them to progress in the tree. You don't need the crazy mitigation that you would for a raid boss to level efficiently. Any suggestions to these builds are great -- I leveled (switching between Fury, Arms, and Prot at different times) with the old trees.