PvP realms in LA are :
Aegwynn
Akama
Barthilas
Blackrock
Bloodscalp
Bonechewer
Boulderfist
Chromaggus
Crushridge
Daggerspine
Darkspear
Dragonmaw
Drak'thul
Dreadmaul
Dunemaul
Firetree
Frostmane
Frostmourne
Frostwolf
Garithos
Gurubashi
Hakkar
Jubei'Thos
Kil'jaeden
Korgath
Malorne
Mug'thol
Nathrezim
Ner'zhul
Smolderthorn
Spirestone
Stonemaul
Stormscale
Thaurissan
Tichondrius

I'm on Akama so I can speak for it, it's about a 1:1 ratio of Horde to Alliance. If you're looking to be outnumbered check out http://www.warcraftrealms.com/realms...hp?sort=server but keep in mind these can be way way off.

EDIT: Updated the list, I was missing quite a few.