Tsakiera is right. The Alliance Artisian LW trainer (teaches Expert, 150-225), is in Darnassus.
As there isn't much reason to be in Darnassus other than the odd quest here and there and for training, be sure to take a few stacks of leather with you. That way you can make several new items while you're there and then pick up all of the new recipes you want. Then you don't have to come back for a while.
As for the specialties, it really depends on the class you play. If you are a Druid, Tribal is best. For Rogues, it's Elemental. Shamans go with Dragonscale.
If you're a Hunter, you're kind left out. Blizzard has stated DS is the way to go for Hunters, but their chosen set (Black Dragonscale) only has four known pieces, and it gives Attack Power instead of Agility. Many Hunters with LW, myself included, dump it after completing the Tough Scorpid set at appx level 45. After that, you're better off picking up pieces of "... of the Monkey" mail off mobs or at the AH.
Tyrian 60----Adaan 40-------Ptosh 23
NE Hunter----Dwarf Priest---Troll Mage