It's been awhile since I was on an ADT as a medical student, but I doubt much has changed. When you get to Ft. Sam Houston you report to Bldg 592 (BOQ/billeting) on main post. They will assign you a room either in the BOQ or in the guest house by BAMC which is walking distance to BAMC. Or, if they are completely full they will give you a statement of non-availability and you can stay in any hotel you want and will be reimbursed up to the per diem amount. They may allow you to have a rental car or may assign you to share on with another med student.