The law's recognition of skateboards as a legit mode of travel may be rare. Didn't check, but don't think state law has anything. Locally, Portland has an ordinance allowing use of skateboards on that city's streets. Some 15 years ago when the ordinance was proposed and adopted, the concept was very controversial. Read about it in this old Ray Thomas-Swanson, Thomas, Coon article:
SKATEBOARDERS AND ROLLERBLADERS GRANTED SAME LEGAL STATUS AS BICYCLISTS IN PORTLAND
Seeing as how your question asks about status of skateboards with respect to their use of the streets in Beaverton
, I'll refer to what reference to them there exists in the Beav's city ordinances. Beaverton city ordinances say the following:
"...6.02.230 Rollerskates, Sleds, etc.
No person shall:
A. Use the streets for traveling on skis, toboggans, sleds, or similar devices, except where authorized.
B. Use rollerskates or skateboards on sidewalks in the business district or on any street, except as authorized or except to cross at a crosswalk. ..." Beaverton uniform traffic ordinances
So generally, use of skateboards on Beaverton streets downtown, isn't legal. Is 5th St in Beaverton's scattered, bi-sected commercial areas actually, 'downtown'? I suppose so, but it's kind of hard to tell what is and what isn't 'downtown' in Beaverton, unless there's an officially designated 'downtown' district I've not yet become aware of, apart from the neighborhood designations. 5th shown in the picture is actually in 'Central Beaverton', which covers other neighborhoods as well. Not that anybody riding a skateboard in Beaverton would have any particular reason to imagine they aren't allowed to ride streets and sidewalks in Beaverton. Quite a number of people ride skateboards on the Beav's sidewalks and streets. Fortunately, they don't much seem to be on the big, dangerous thoroughfares, Canyon and Beav/Hillsdale, Cedar Hills Blvd. They're in use on neighborhood streets and sidewalks though.
People obviously are using skateboards for transportation in Beaverton, so the city probably would be smart to recognize the boards as legit transportation in a way that would better, encourage people using them on the streets and sidewalks to do so through basic observance of basic traffic laws
That section of Hall you were on can at times, allow bike traffic to roll at a very fast clip. Folks riding or skating counter-flow in the bike lane is potentially quite a bad situation.