If you plan on working in NYC/DC or LA, I would say to get rid of WUSTL and ND. They are both great schools, but BC and BU seem to be quite portable degrees into two of those markets (NYC especially, DC somewhat). From all these schools you need to do quite well to go to LA...so why not go to BC or BU (where, if you do not manage top 10-25%, you can still go to NYC or DC).
As to the BC/BU debate...they're completely comparable. Neither will aid you in your pursuit of "international law", but will have some classes or clinics geared toward that. The general consensus has been that BC does marginally better in Boston and BU does marginally better in NYC...take that with a grain of salt.
As for the better part of the city belonging to BU...I'd say it depends on what you are looking for. BU is more accessible to downtown, but the law school itself has pretty atrocious facilities (but fabulous views). BC is further out, most people have cares, but the facilities are pretty amazing and the campus is quite nice.
My advice: visit the four schools and see which one you feel more at home with...they each have a different feel. Also take into account $$. They are all good schools and offer comparable employment stats. Don't let people sway you with them saying "GO TO SCHOOL X...IT'S THE BEST" when they, themselves, actually attend School X. It's not exactly impartial.