I feel pretty bad about both of your current top two choices (Bellingham or Peekskill) because they seem too far from major cities. I worry this distance will seriously hamper your ability to hire good people, which is arguably the most important thing MIRI needs to be able to do. [Speaking personally, not on behalf of Open Philanthropy.]
To expand on this a bit, I think that people with working partners would be the group most likely to be deterred from working at MIRI if it was in either Bellingham or Peekskill. The two-body problem can be a serious constraint, and large metro areas tend to be much easier to find two jobs in. That may be getting better with the rise of remote work, but I do think it’s worth keeping in mind.
Less of a constraint if matters are arranged such that living in NYC is practical. Expensive, of course, but no worse than the Bay. It’s a long-ish commute, but not too terrible by mostly-empty train (the full trains will be running the opposite direction). Easier still if WFH a few days a week is supported.
I think moving to the country could possibly be justified despite harms to recruitment and the rationality community, but in the official MIRI explanations, the downsides are quite underdiscussed.