If you are a good candidate for admission to one of those schools, then apply. If you are fortunate and a good candidate, you may have the privilege of a choice; if you don't get accepted, at least you won't be asking yourself later what chances you might have had.
As for borrowing hugely for undergrad school, be very careful. Harvard, Yale and Princeton have big endowments and robust financial aid programs so you may not do so badly going there as opposed to many state universities whose endowments are lesser and whose "sponsoring" states have cut funding. You might end up with a less marketable degree and nearly as much debt going to a lesser school.
If you are shooting for the top Ivies, you ought to look at other schools in the same general class: Penn, Dartmouth, Duke, Stanford, Columbia, Brown, Cornell, Northwestern, University of Chicago and Johns Hopkins. And you would be foolish to discount the premier state universities, particularly Berkeley, Michigan, Virginia and U. Texas Austin. Most of those are very highly competitive and very well endowed. Of course, you could also be very shrewd and go to a less famous school, do very well and move on to a nationally-known school for your graduate studies. Whether you go to a top Ivy or not, you will have to do well to be competitive for a place in a good medical school. Leaving yourself the freedom to choose either a civilian medical school or USUHS without having to consider the weight of substantial undergraduate debts is undoubtedly a better strategy than feeling you must favor USUHS for financial reasons.
