Nationwide polls have already shown the Pacific NW to be the least religious, so combined with the Bay Area, yeah it's definitely the PacWest.
That was probably true until the mid 2000s. It seems like New England is playing to win: http://articles.latimes.com/2009/mar/16/local/me-beliefs16
"New England surpasses West Coast as least religious region in America, study finds"
I feel like the Pacific Northwest (in other words excluding California) would still be less religious than New England. Also would it would probably be closer in population, grouping the entire West Coast together like that is crazy.
Just exclude Southern California actually. I think the Bay Area is just as irreligious as the Pacific Northwest. Socal on the other hand....