The most valuable gift I received from studying abroad in Spain has been the ability to speak Spanish. Coming from California, it only seems logical that I learn the language. Plus the reality is not everyone in the United States does speak English, and speaking another language can be extremely useful.
Plus if you and your friends speak the same different language you can talk smack in public and no one will ever know what youre talking about. Secrets are even easier to keep too, if no one else at the table knows what you are talking about. Need to save your home girl from a guy that she may or may not want to hangout, just ask her if she is okay in a different language then proceed accordingly.
Also being bilingual opens you up to new cultures. Being completely immersed in the Spanish culture really helped me develop an understanding and acceptance for ways of life different than my own. The food, music and just way of life is completely different than the way we work in America and I think that by learning the language, in my case Spanish, you really take a part of the culture with you.
So if you are thinking about learning a second language please do because you will learn more than just words and sentences but also an entirely different culture. And if you want to take it a step further go visit and live in that country because to be honest you will never really fully grasp the language, culture and overall experience of learning another language unless you immerse yourself into the culture.