High School languages? Which is the most helpful to take?

I originally wanted to take French or German, but after the constant nagging of my friends, I've begun to reconsider my choices. My school offers French, German, Spanish, Sign-Language, and Chinese. I want to travel to Europe, but I also want to be able to use whatever language I take after high school (we have to take a language all four years). Suggestions? Comments? Any help appreciated.