You have to get the Chinese client for mac up to date and follow the manual patching guide. But instead of using the *.exe files in the downloaded archive, use the equivalent files from your Chinese client.
Or use Bootcamp
Edit： I didn't find any downloader for an OSX Chinese client. I don't know mac os at all, but I think there might be some windows emulator you could use, though your game might need more resources to run. I used something similar to play wow on linux. But the best solutions is either Bootcamp, or Taiwan servers because you just need to modify the realmlist.wtf to play there.
When you log on a realm type "/join english
" to get in touch with the community members.
WoW English/Chinese glossary
(2000+ translated words) found on wow-in-chinese.jfs-web.chEnglish speakers are consolidating on the same realm for Cataclysm check this thread