Withdraw from schools as soon as you know there is no way you would conceivably attend them.
Georgetown comes to mind as more expensive than Sinai, Tufts even more so, and I don't think either of these schools offer any really unique global health opportunities unless you are really interested in public policy and advocacy, in which case you might want to hang on to Georgetown.
I am interested in global health as well (not sure if I'm going to end up pursuing it, but it's definitely my strongest interest within medicine right now). One thing which seems exceptionally important considering this interest is attending a school which will provide exposure to a very diverse patient population so you get used to seeing patients with odd diseases and from very different cultures. BU is good for this because Boston Medical Center is the safety net hospital for the entire city of Boston, and BU has a big commitment to service. I'd hang on to BU. All the NYC schools are better than average in this regard as well, and NYU has Bellevue, so I'd keep NYU. For the same reason, I would dump the schools that are in more rural areas - Rochester and Dartmouth (even though Dartmouth is an Ivy, considering its location, I'd much rather go to Sinai - but that's a rural vs. urban personal preference thing).
That being said, at this point, your chances of getting additional interview invites are dwindling, so you might not want to withdraw from anywhere and see what happens.