Yes, that is the ideal blast fallout footprint. On a more realistic basis, the prevailing winds and the Rockies, Blues and Steen mountain ranges should aid greatly in preventing most of the worst of it from reaching quite that far into Oregon and Washington. When St. Helens blew, I wasn't living that far away, and yet the only ash exposure I received was what went around the planet once. I was less than 80 miles from the eruption at the time. Granted there's a lot more energy expected from the Caldera eruption, but that is still going to be a whole lot of atmospheric energy to have to overcome. Given that Nuclear fallout maps from GZs all along the west coast show virtually no plume extending into SE Oregon, I'd say it is a fair trade-off. Given the sheer volume of ejecta that would be put into the atmosphere, I would think that what gets deposited in Oregon will be not much greater than average global depositions in the northern hemisphere anyways.

There's always a chance that large destructive media might make it that far, but I think propogational losses will be great enough at that range that it should be negligible compared to the general hemispherical threat of coverage of fine particulates. 1200 cubic miles of ejecta, most of it being fine particulates able to stay suspended in the atmosphere, will be the most likely hazard to deal with.

However, the caldera is only one factor of many to consider, and given that most of the others are relatively so low in occurence and effect in that region, especially the most frequent sort, I concluded SE Oregon would be a relatively safe, if not inconvenient, haven.