"Operating" as in "riding" or as in "surgery"? The latter might lead to a malpractice issue...

I wouldn't try it.

If you're not charged with a DUI, you could get charged with endangering an animal or public drunkenness.

https://youtube.com/watch?v=_yWFPrG_Zl8

I don't know about Washington, but as far as I know, in most states, the DUI laws are written very loosely around anything with wheels. So the most extreme interpretations only go as far as including everything up to walking in heelys with the roller wheels retracted would technically count. They'd probably hit you with anything though. Drinking in public is a lowest social class activity, so painting the perp with any color interpreted law is likely fair game to the motivated orator.