For what it's worth, I am somewhat in the same boat you are in. I'm 19yrs., turning 20yrs. this March, currently working on a CJ degree.
While I haven't smashed a mailbox, I admit to having a couple underage drinks in my life (nothing serious, but nevertheless illegal); my record isn't exactly spotless either, so I feel as though I can relate. It would seem the general consensus is that as long as you stay on the straight & narrow, stay focused, and get a little college (or military) experience under your belt, you should be good to go as long as you haven't done anything that would really otherwise disqualify you. That happens to be just what I had picked up from reading on the forums though, so I can't speak with any authority on this matter.
A few of my classmates have fairly... "wild"... aspirations that they hope to meet in life; enlisting with L.E., while at the very same time admitting they outright abuse prescribed medications, drink heavily, engage in less-than-honorable acts, etc.
From what I'm hearing, you aren't THAT bad off. Good luck!
Four noisy cylinders don't have the soul of eight cylinders playing the tune that my right foot orchestrates.