It seems to be widely overlooked, but interviews are a two way street. Interviews are designed for the medical school to see and evaluate the person, as opposed to simply evaluating the application. Reciprocally, going to interviews is an opportunity for applicants to evaluate the medical school, as opposed to simply reading about it in a catalog, brochure or word of mouth (akin to asking for opinions on SDN). Otherwise, medical school application is kissing cousin to going on blind dates. You pay your money and take your chances. If you like surprises, blind dates, going to interviews and skipping out without doing your homework, then save your valuable time and money and accept a regional interview.
I can understand if the cost of going to an interview is really beyond your means, but look at it this way: its the quality of your future at stake here, and a little extra investment (and debt) may be worth while. Otherwise, you should have taken this into account when you were applying to medical schools: was it essential that you apply to this distant medical school?