Help Me Choose a Language to Learn.

I live in the United States. I am fluent in English. I know nothing of any other language. I would love to know what the most useful language will be in the future. I'm going to be dual-enrolling soon at a local university, and I wanted to take a class which is unavailable to me.

Can you suggest a language? The only classes currently available to me through my high-school are Spanish and Latin.

Chinese(Mandarin) because its gonna be very important in the future and many people speak it.
Spanish because... many countries in the continent speak it.
French because like Spanish and English, many countries in the world speak it.