Let me start with a little civics lesson. The U.S. is a constitutional republic and the laws are different for each state. Anyone who says they know the law is hopefully talking about Washington State, where the OP is from, because that's the only law that applies in this case. Here is how it reads:

RCW 46.61.770 Riding upon roadways and bicycle paths.
(1) Every person operating a bicycle upon a roadway at a rate of speed less than the normal flow of traffic at the particular time and place shall ride as near to the right side of the right through lane as is safe except as may be appropriate while preparing to make or while making turning movements, or while overtaking and passing another bicycle or vehicle proceeding in the same direction. A person operating a bicycle upon a roadway or highway other than a limited-access highway, which roadway or highway carries traffic in one direction only and has two or more marked traffic lanes, may ride as near to the left side of the left through lane as is safe. A person operating a bicycle upon a roadway may use the shoulder of the roadway or any specially designated bicycle lane if such exists. (2) Persons riding bicycles upon a roadway shall not ride more than two abreast except on paths or parts of roadways set aside for the exclusive use of bicycles.