At low level its probably better to concentrate on one talent tree to get the most benefit from the few points you have. Coming from being a hunter I went Demonology as it felt more comfortable and kept those nasty mobs from hitting me (some of the time).
At 25 you have Ashenvale, Stonetalon, Duskwood, Wetlands available
By 30 you can open that up to Hillsbrad, Arathi Highlands, Desolace, Altarac Mountains, and of course the brain-numbing Stranglethorn Vale
Full List Remember there are Warlock trainers at Ratchet so if you're Alliance in Ashenvale/Stonetalon you don't need to cross over the sea to train.