keep your US wow. There is a very simple and quick way to play WoW on a chinese server, still using your Us version.
Leaqrn chinese though; WoW is nonetheless a social game, and not being able to communicate will alienate you somehow. Simply depends on how deep you wish to get in the game anyways. But, learn chinese asap. It'll help for the game and IRL as well.
the "card thing" is related to the payment. here in china, wow works like a prepaid mobile phone. you get a card, scratch off a number (you can also buy a number online, so you dont need to move your lazy bum at all. it's what i do), you hack in that number on a website, and BAM, you get another 66hours of gameplay... so yes, you'll need cards. these same cards will get you CD-keys as well. Like a prepaid phone, you only pay for what you play. meaning if you charge 66h into your account, and you play 2 hours, then dont touch your toon for 4 months, after 4 months it'll still be there, ready to be played for another 62hours. each recharge is valid for 1 year. they do stack.
check the forums for how to gte a valid cd-key and where / how to get a card. if you cant find it or you are somehow not sure, pm somebody or me, and somebody or me might help you out with it.
me going to to NJ next week (and basically every week) to meet clients over and over again.... should have a beer some day.
HAPPY NEW YEAR
Come and join on Starcraft 2 as well =]