Just put up a some simple text: "If you'd like to help translate this site into your language, please feel free to drop me a line at [email]. Thank you!"
I like it! Crowdsource it. I'd probably want to have at least two people do it independently per country to make sure they aren't saying naughty things.
You can also check their translation by putting it back into English with an automated translator. (Google has one for example.)