I would not recommend open carry anywhere in Washington. Why? Because the level of education regarding what's legal and what's acceptable with law enforcement here is, ah... varied.
In the right place, with the right LEO, open carry is fine and dandy... with the circumstances turned, you,
at best, get your gun confiscated and a date for court.
Although this would constitute breaking the law and is put forth purely for
entertainment... if the gun is well concealed on your person, sufficient that it does not print and would not be seen even by a trained eye... you might want to consider concealed carry.
(If you carry a full size .45 under a tight t-shirt... forget it.
)
My perception is based on the fact that I've carried legally in WA state nearly every day for over 15 years, and have never been given a second glance (to my knowledge) by anyone, anywhere... and this includes being in close proximity to large numbers of LEOs at one time.
Granted, I generally don't look or act like a suspicious person, but rather "Joe average" going about his daily business... which goes a long way towards being invisible.
The visible gun can cause anxiety in others. A gun unseen is...
not a gun. Successful concealed carry is a form of "social camouflage".
The option is to leave the gun at home and enjoy your trip knowing that the likelihood of you actually needing a gun is very, very slim.
C