Start speaking jibberish to him, a foreign language he's never heard. Then, typically start getting upset and angry, (wave your arms around too) when he doesn't understand. He'll just go to the next house, hoping they understand English.
Nope, he'll break out a booklet that has basically every form of writing for every language on earth in it, and try to get you to identify which one you're speaking.
Then he'll either hire a translator for that language or find someone in the Census that speaks that language and keep coming back and do the interview in translation.