I completely agree with your points about cars, but I don't think Portland is in the running here. I am wondering what other areas may be most walkable, livable without a car. The US is such a car-centric place, that it's tough. Europe would obviously be much better for that.

Singapore seems too socially conservative, though.

Some more fuel for Austin:

While the comparison is not made directly in this article, I think there is somewhat of a tick vs. mosquito trade-off being made specifically between the NY/Peekskill and Austin sites, given that NY is just barely out of the mosquito area on that map, and Austin is right in it.

But I mention this to say, as a native Southern Louisianan, I'd be far more wary of getting Lyme disease than being bothered by mosquitoes. Mosquitoes, while sometimes annoyingly resilient to repellents and things, are simultaneously rather fickle ~ a slight breeze or minor change in temperature is enough to dispel them. 

That includes the fact that they're only seasonal, and when they are around, changes within a single day offset them.

And if MIRI staff want to spend significant time outside, the Austin area offers ample space in literally every direction outside of Austin proper.

And yes it gets hot, but Austin's location in Central Texas puts it just outside of that very dense, humid climate of the Southeast. Even the Northeast, including NY, is pretty humid and dense.

And the latter is not always bad, but Austin has that Western, desert, dryer air, which will be familiar to Californians, and which many people find not as taxing.

(Insert "It's not the heat, it's the humidity that gets ya" cliche here ~ but it's true!)

It's a physically beautiful area, too.

I understand you haven't necessarily found a specific location around Austin yet, but it's there somewhere.

Sounds like the Washington State option isn't that appealing, even though you have Bellingham on the list.

Scott Alexander recently pointed out that some of the same problems apply in the Cascadia region as exist in CA, even though it's a bit cheaper. And it's just a bit colder, too.

And all the other locations are seemingly more minor options.

The South, Texas, and Austin are all growing overall, for lots of reasons, and being around Austin puts one near all that growth and dynamism of the Sun Belt, but still not enveloped in either conservative Deep South culture, nor in the path of potential hurricanes, which the rest of the Southeast, including nearby parts of Southeast Texas, are at risk of. Austin is just far enough for the strongest of hurricanes to have died out rather well by reaching that point.

Plus, I mean Austin is one of the growing major tech hubs, Houston and Dallas are working on a high-speed rail between them, and that could eventually grow to include Austin and San Antonio. 

And Houston and Dallas each have major airports, both of which are some of the most well-connected and international in the world.

And Austin is likely to get more flights as more demand develops. Word is Delta may make it a hub, but I'm not sure about that.

And being in Central Texas, it's very conveniently located to travel to anywhere else in the US, as opposed to being all the way on one or another coast or in a far quadrant.

And no state income tax, just like Washington.

Lastly, being on the cusp of the West, if anything goes awry, sociopolitically or otherwise, the capacity to shift toward West Texas or even further, and holdout elsewhere, seems much safer, spatially and logistically, than being in a relatively crowded place like the Northeast. Although this is perhaps more subjective than my other points.

And you all don't have to be in Austin proper and deal with high rent and traffic. You can just go there when you want or need.

I'd chalk up this comment to another vote for the Austin area.