I like to draw from my head, and Im worried about college. Will my unwillingness to draw still life hinder me?

Great self awareness as an artist. I was talking to an illustrator for children's books just the other day and we talked about just this. We both agreed that it is entirely normal and most artists go through at least some level of this. As for your second question, the mastery of realism, I would say no, you certainly don't have to MASTER it, but you need to work on it. Learn the techniques, learn to be open as an artist. If you put your cartooning aside and work on realism, you will be amazed at your cartoons when you get back to them.