Being from Pittsburgh, I try to show versatility in my work. I mostly focus on one style, but I like to show clients my ability to illustrate all subjects. But, the lessons you learn from other people who are more experienced really are invaluable. You learn new techniques that maybe you would learn someday, but probably not. I would definitely recommend going to art school.
Nobody knows everything.
Learn from others and observe their techniques. I was forced to go to a more affordable college. A number of the faculty members of my high school art department were Indiana graduates, and they helped me decide. The school has to be right for your goals. If you, as a student, want a career in graphic design, then look around and find the best college or school for what you want to be.