I was also a ROTC cadet, and I looked at USUHS as well. You would probably be a shoe-in for an HPSP scholarship, so I wouldn't worry much about funding for medical school. It'll be covered some way or another.
What I WOULD worry about, however, is getting in. Since you are scholarship ROTC, you will be commissioned immediately after your last semester and given your orders to OBC. You can try to get an ed-delay when you fill out your accession packet, but the chances of getting one without an acceptance letter from a med school are slim. I tried for a delay when I accessed, and put down medical service corps as my second choice-- I didn't get the delay, but I was accepted to a medical school the following spring. So, with my acceptance letter in hand, I filled out the 3 or 4 forms needed to request approval for an educational delay to attend medical school-- mine went through about 3 weeks before I was scheduled for OBC. It was an interesting and stressful process, but it worked out for the best. Lemme know if you have any other questions..
take it easy
homonculus