I know in parts of the US it is illegal for bicyclists to ride their bikes on the sidwalk. I've been seeing it a lot in Seattle, WA, US and not sure if it's allowed.
Section 11.44.120 - Riding on sidewalk or public path
So I'd say it's legal. Have fun!
It would seem that cycling on the sidwalk in Seattle is legal:
-- Regulations for Bicycling and Driving with Bicyclists, Seattle Department of Transportation