So I cant speak directly to the foreign students question, but from what I have gathered it seems to be extremely difficult for foreign students to get into american med schools though I am sure there are a few. I think it is a question of numbers...there are 30,000 american students who apply to med schools, whereas in PhD programs there are not nearly that many. I think it is particularly telling that I have heard the NIH has grants for post-docs, but there are not enough american post-docs to use the grants! Of course, it could be that there are PhDs who chose to go into industry....and this is all coming from a physical and biomedical science point of view.
As for the post-bacc v. CC issue...There is a big difference. Post-baccalaureate programs are designed for people with bachelor's degrees and are found at 4 yr institutions. There are some people who have taken pre-reqs at CCs while enrolled at a 4 yr school and gained med school admission with no problem, but I think that if you are have your degree if would behoove you to do a post-bac or some other graduate level work (maybe a MS, as I did) to satisfy reqs. It sounds to me like you are making a change from your initial degree to pursue medicine...there are several post-bacc programs that are geared especially for ppl in that situation and there are some which are geared to those who have the pre-reqs but need to improve their grades.