which spec to level right now?

I just started this character and got it to level 10 should I be going fire or frost?
Try each, figure out which you prefer. That's what I think you should do.

However, frost mages, with their water elementals should still have an easier time than other mages, especially seeing how they get slows sooner than the other two specs.

Though arcane does get an instant cast, which is nice while kiting.
Once you hit 20 (which will be in an hour if you push hard) you'll have Arcane Blast, which makes Arcane superior...no need to slow the mobs with a Frostbolt because they die before they reach you. Plus you get a 25% arcane bonus, which boosts your 100% mana free Arcane Missiles. Ultimately you should try them all once you reach the 30+ mark, so you have some talent points to play with. But if you want the fastest, most dominant leveling spec, it's Arcane.