My friend, you are young, you are in one of the best cycling cities in the states (for both year round cycling as well as cycling awareness and support), and you have an interest. Go for it. I promise you that unless you suffer major incident, you will only get better. You might not win your first race, but don't be afraid of it either. Let us know how it goes. (By the way, what stretch of the Burke are you talking about? I am trying to think of a stretch that has any sort of lengthy 4% grade and I am not really thinking of it)