I leveled 8 of my 11 level 90s from 85-89 via pet battles, simply hitting all the pandaria pet tamers once a day (By using a 2-team for each trainer and a leveling pet, I also got a significant chunk of my 140+ level 25 pets this way).
I chose to stop at 89 instead of going all the way to 90 in order to give me an opportunity to get rid of my cata gear and to get a quick refresher course in how to play it.
But, then again, I'm also the kind of person who likes dailies, so what works for me might not appeal to you.