Do you speak their language?
That is always a good question.. only a quarter of the people who speak English do so as their first language. It's always good to talk to people in their first language where possible but a quick look back at language data suggests that the languages people frequently speak as not first language are: English; Hindi; Russian; French. So, for example others like Chinese, for the most part is spoken as first language.
Which begs the question.. where is the Hindi forum?.. Perhaps there's a market there??
Also there are simple ways to capture non-English speakers and redirect them to a message specific to them. I have a simple script
for doing that in PHP which might be good for that - add an element to the header of the page even, rather than full redirect asking for their help engaging that languages users.