i used the AOA website to find a family practice DO. i can't stress enough how much precious time you waste by not sending letters to the DO's office. you can cold call all you want and wait for a call back but most of the time the receptionist won't even pass the message along to the doctor.
i wasted weeks just cold calling and then finally took the time to write a short cover letter explaining my interest in shadowing. i attached my resume as well. later that week i had 3 doctors calling me back. i sent 10 letters total and some never responded. so in my opinion, start sending some letters! it doesn't hurt!
good luck!