Normally, you get about 3-4 experiance per kill when in a raid group in Alterac Valley, making killing things almost worthless. But, there are two ways to make them give 670 XP instead of 3-4 XP per kill.
#1: Type /afk and use the disconnect macro at the same time. This makes it so when you log in, you are not in a raid group, but still participate in the BG. This means you cannot get the raid penalty, and you can kill and get all the experiance you want. You should also be getting XP for tower caps and wins.
#2: Get distance from your raid members. About 100 yards (Sight) or 150 yards should do it. If you are close to a party member, you will get the party penatly (50%). If you are close to a raid member, not in your party, you will get the raid penalty (90% less xp). But, with distance, you can get full XP, as seen in my screenshot.
WoWScrnShot_010110_142946.jpg picture by 8u3jc - Photobucket