I was making these for personal use and thought I might share them here since (to my knowledge) nobody has posted visual maps of the pet levels. Most of the information on these maps came from this forum (thanks to everyone who posted that information!).
I'm fairly sure there aren't any pets in any of the Vashj'ir zones. The level listed for Gilneas is for the Ruins
of Gilneas, not to be confused with the starting area for Worgen which is only accessible if you're a low level Worgen. Goblin, Worgen, and Pandaren starting areas have no pet trainers and no wild battle pets to catch- you'll have to leave their starting areas before you can starting battling/catching pets with them.If you'd like to see a larger version of the maps, just click on them (there's a link below each map for anyone who has images turned off). If you'd like to see a text-only version, hop on over to this list (Made by Shadev).
I'm sure I'll be correcting these and adding more to them as time goes on, so remember check back again sometime if the information you're looking for isn't on the map yet!EDIT 10/14/12:
My apologies for taking so darn long to update these. Just got back from a six day trip into the wilderness where no technology could follow, lol. Everything should be accurate now but if it isn't, leave me a comment and I'll update the maps.
------Eastern KingdomsMap of Eastern Kingdoms w/ wild pet levelsKalimdorMap of Kalimdor w/ wild pet levelsthe MaelstromMap of The Maelstrom w/ wild pet levelsNorthrendMap of Northrend w/ wild pet levelsOutlandMap of Outland w/ wild pet levelsPandariaMap of Pandaria w/ wild pet levels