rball,
I have to say that 6'4 and a 6.6 60 and you are walking on at a school where you haven't contacted the coach seems odd. On the other hand, I know Chris Lambert got signed by BC just before school started, so anything is possible.
If I were you, I would be emailing and calling the coaches and telling them you are coming. Would advise them the offers you have received and from where. Walking on, sight unseen is an enormous gamble. With the stats you describe, (I trust you can hit), a lower DI head coach should be ready to hug you.
Also, make sure you show up in the best shape of your career. That means physically in the best shape of your career and baseball wise the best shape of your career. You are starting at the bottom, or below. You need to prove, before the coach sees a single player, that you are different.
Finally, if I were you, I would be in contact with TRhit. If anyone can help you, with the way you represent yourself, he could. Bottom line, as has been posted, walking on is extremely problematic. If you really want to play, minimize the risks by letting the coaches know now who you are, that you are coming, and how you play the game. Make sure you are in the best, most competitive shape of your life. Contact TRhit for any advice/help he might give. Finally, doing everything you can to make sure you are the next Chris Lambert, or the next best player behind him.