By knowing English, you can communicate with most of the world, because almost every country teaches English as a foreign language. For example, more than half of the popuation of Europe can easily communicate in English. I've seen that in Netherlands they already prefer English to Dutch when they talk to each other.

I know 3 foreign languages and I think it's a waste of time to learn more, because if a person is not literate enough to communicate in English, I have nothing to talk to them about.