You can ski and snowboard, but you can't impede traffic (if there is any) or violate other traffic laws (e.g., you must stop at stop intersections, you can't violate right of way laws, etc.).
Also, police regularly cite pedestrians and bicyclists for infractions, so there is no reason to believe that a person on skis or a snowboard would be treated differently. Have fun but be vigilant!
Legal and no speed limit! There must be a god in heaven! You would be liable for damages to persons or property if you cause some damage, but that's the way it always is with skiing.