I haven't played WoW in a while, but WoW builds are constantly changing. Because of this I think you'll find a constantly updating source helpful. I always found great information at Elitistjerks, mmo-champs and even in the wow-forums.
This a good guide for rogues in cataclysm. His update is from this month, so I believe this is a accurate guide.
Some good sample here, here and here
Ok some explanation now:
Why subtlety:
Subtlety rogues present a combination of DPS and utility
allowing them to do well in both PvP and PvE. In the DPS race an
Assassination or Combat build might pump out more overall damage, but
Subtlety is more fun and more flexible. And Assassination doesn't have
Shadowstep.
Subtlety rotations:
PvP:
There is no PvP "rotation." Try to lock up your opponents and burst
them down when you can. Glyphed Garrote silences casters Keep
Recuperate up at all times. The HAT talent helps with this, providing
extra combo points. You might even be able to start a fight with Recup
running. Try to keep Slice and Dice up, but not at the expense of
stuns. Rupture is good Vs stealthers. Learn to use Shadowdance and
glyph it (two more seconds.) Save your Shadowstep, if possible, until
the opponent escapes (eg: Blink,) then use it to catch up.
Check out the links. they are more complete, with Gems, runes, professions even races.
Sorry for the link only post, i used to see some http://jsfiddle.net/ posts on stackoverflow, and i like post the font with a link, by my mistake (was late) i forget post some content with it. Thank you for your -1
As a rule of thumb you can follow these priorities:
PVP(Sub): 5% Melee Hit > Crit > Haste > Mastery > Expertise
PVE(Combat): 8% Melee Hit > Expertise (26) > Haste > Mastery > Hit(up to 27%) > Crit
You can look for suggestions on places like Elitist Jerks then try various setups on online tools like Ask Mr. Robot
Anyway you don't need 8% hit for PvP, the hit cap against other players is 5%. Take a look at this guide on the official forums for a lot of useful suggestions for PvP, regarding not only equip and spec, but also glyphs and abilities priority.
For PvE you can read this other guide on the aforementioned Elitist Jerks forum.
Best Answer
The Alliance PvP vendor is in the Valley of the Four Winds, roughly here:
There is a FP next to it, so if you track that on the minimap should be easy enough to find. They are inside the tower.