Nevermind. I found a workaround. I just copied the vlc.mo file from the locale/en_GB/LC_MESSAGES to the locale/zh_TW/LC_MESSAGES folder. THEN I could locate Settings/Preferences/interface/language (scroll menu)!
As a note to the developers: it might be useful to ASK the user what language to install in, instead of auto-detecting the system settings (which could be set to the default displayed choice). Of course, if the question is in the same language as the default settings, and the installer cannot read that language, well....
![Sad :(](./images/smilies/icon_sad.gif)