Re: What language ?
Business wise ( I'm a head hunter, IT) I would say Spanish or German and the bigest one moving forward will be Chineese. They will own the US shortly, and it will be very huge in demand.
If you can speak bi or tri you will have a great shot at a great job. "Just english" is a handicap, think global for the next 10-20 years, the rest of the world already speaks more than one, just America that isnt so much.