Anyway, Lemur, learning a language beyond the basics takes rather more than two years. Ten is nearer to the mark.
But don't you also agree that it kinda depends on the relationship between your native language and the language spoken in the country you're living in? I mean, German would be a lot easier for the English to learn than say Russian, Arabic or Farsi. Same with Japanese and French, for example (the horror..).

I'm with Idaho, although I do believe that learning the language of the country you've moved to is something the government should enforce. Either fining or subsidizing people that respectively don't and do try to actively learning the language is very important. It'll help to close the gap between immigrants and the native population.

On the other hand, especially with the immigrant laborours, who do not wish to stay very long, speaking your own language is a natural thing; the farther people get removed from their roots, the stronger their resolve will be to get back to those roots. Language, religion(!), food and such things are all parts of their culture they've taken with them and wish to cling to as well.