Dear Chris, I think that the size of the hotel and ability to handle a
typical LLL crowd is a major deciding factor, also off-season rates.  I'm
sure someone at LLLI can give you the particulars.  I had heard in the past
that not many single hotels can     handle that size crowd.  When you
change to using a convention center and several hotels the logistics with
babies and children gets out of hand,  which isn't such a problem for
groups like APHA, who can use the convention center sort of facilities.
Personally I'd love to come to the PNW, having only been there once in my
life to Oregon (they took me to dinner in Washington State :-)  Sincerely,
Pat in SNJ where it is cold in winter, hot and humid in summer, but spring
and fall are decent!