I was able to find where all of them are located, except for the two new ones in Pandaria. For some reason, I didn't find any wild companions in Pandaria, new or old ones.
The Crow which can be found on the Darkmoon Island also can't be previewed atm, since the faire is currently not in town on the PTR.
Here's a list of where all the new wild pets can be found:
Anodized Robo Cub -  Winterspring (Around Everlook)
Arcane Eye -  Deadwind Pass (Ruins outside Kara)
Cogblade Raptor - [18-19] Blade's Edge Mountains (Outside Toshley's Station)
Crow - [3-7] Darkmoon Island (Around the island)
Darkmoon Glowfly - [3-7] Darkmoon Island (Around the island)
Emerald Proto-Whelp -  Sholazar Basin (The Savage Thicket, where the larger red proto-drakes are)
Fluxfire Feline -  Dun Murogh (Outside Gnomeregan)
Harpy Youngling -  Northern Barrens (The Dry Hills, where the harpies are)
Infinite Whelpling -  Caverns of Time (In the area leading down to the main cavern, and the main cavern outside, NOT inside instances)
Lofty Libram -  Hillsbrad Foothills (Dalaran Crater)
Nexus Whelpling - [20-21] Coldarra (Borean Tundra) (Coldarra island)
Stunted Yeti -  Feralas (Where Feral Scar Yetis are, south of DM)
Also, since the Pet Journal preview of the Infinite Whelpling was bugged when I was gathering screenshots of all the new pets, here's a better preview of this little guy.
Pretty cute! It's one of the most unique whelpling colors to date imo. :)