I'm not actually in Seattle, but in the surrounding metro area, within easy bicycling range of the city.
I don't know if any one person could answer that question, unless they perhaps worked at the DMV. But I'm sure there is a good population of Prius Owners in Seattle and surrounding suburbs.
I will land at SeaTac Oct 15, spend a week in western Washington (Montesano, Bay Center, but mostly Bellingham) and fly out Oct 22. If there was a day in Seattle being Priusy, my wife is an architect and would get to see City. Last time we got a City Pass. Official Seattle CityPASS® | Visit 5 Seattle Attractions for $79