Funny thing is you only need to know 6 Cantonese words to get around Hong Kong too:

Ngo mm zi lei gong me (BTW I am actually half-Chinese if you want to test the veracity of this post)

Basically it means: "I don't know what you're talking about"

EDIT: Here it is for no reason in Mandarin: Wo bu zhi dao ni shuo shen me