If you want to do IM, you definitely want to do your core IM rotation at a site that actually has a residency program. This way you can get letters of recommendation from faculty, you'll understand the teaching hospital "dynamics" necessary for residency, and you can discuss the hospital during your residency interview if the topic comes up. I went to NSU-COM and did my three core months at Mt Sinai Medical Center, which has both an ACGME and AOA IM program. I felt that it prepared me very well. Can't really comment on other sites since I didn't rotate at them, but NSU has other rotation sites at Broward General, Palmetto, and Largo, all of which have AOA residencies as well.