Is Protection a viable leveling Spec?
Any other tips for leveling a Pally?

Depends, if you want to level by questing, then its shit. But if you level by doing instance, then yeah prot is the best.

If you solo leveling, do it as ret. If you got tank mate / dps mate, you can do holy pally (grinding instances). Best is have dual spec, one ret one is holy/prot, so when you waiting for dungeon que, you can questing.