With the new patch that just came out today (6/28), the wild pets that you can battle have a paw print icon (the same green one as on the minimap) just above their nameplates.
Oh, and the trainers only have the Pet Battling skill and the racial pet available to train (albeit still at level 91 ). The Battle Pet Healing and Battle Pet Tracking abilities have disappeared (one is available from an achievement, I believe). Although, I do need to check with one of my characters that doesn't have the Pet Tracking ability to make sure it is truly removed from the trainers...