Originally Posted by
MSPeconomist
Unless one is confident of knowing a foreign language extremely well, it would seem risky to go through immigration and customs processing in some foreign language. This is not the time to practice your language skills.
I don't always have the opportunity to converse in certain languages - Japanese and Indonesian come to mind - so when traveling, passport control is the first place I use them. There has never been an issue (but I reckon it also helps to be from ____ country).