Other than in or on a vehicle you can OC anywhere you can CC. Schools, bars, post offices, federal buildings, the secure parts of airports, police stations, jails and mental institutions are off limits. If you are asked to leave a business simply do so or you could be charged with trespass.
Have fun OC is generally not a problem in Washington.
Keep in mind the 1000' federal school zone laws, I think this will be something we will see being enforced in the near future.
I used to OC in an IWB holster all the time, if you can see it it is OC.