Some tips for F2P 19s:
Since you have some disadvantages, you need to make everything count, so I'd suggest choosing your race as to optimise your survival:
Horde:
Tauren
Warstomp is godsend to stop a rogue damaging you, to alleviate pressure in general. Tauren also has an HP bonus, wich you'll need since you'll have about 250hp less than a P2P Twink.
Tauren covers all classes except Rogue, Mage and Warlock. For those, you are free to choose any other race, since they are all balanced. I would recommend Blood Elves for Rogues tho, so you can enchant your cape with +1 agility (Blood Elves have +15 to enchanting so they can get to 115)
Alliance:
Night Elf
Elusiveness helps a lot, since everyone has +2% chance to miss you. Shadowmeld can also be a great defensive cooldown, you can make a melee untarget you for a while and can cancel an enemy cast that's target upon you.
Night Elves covers all classes except Paladins, Shamans and Warlocks. For these, I'd recomend Dwarves, for their -10% damage taken activated racial.