Of course going faster than the speed limit is speeding regardless of what you're riding. You are a pedestrian. Pedestrian laws apply. You can get a ticket for being in the roadway or blocking traffic. Check city, county and state laws.
Most states have their vehicle codes posted on the Internet.
Since 1994 I have encountered numerous police officers but have never received a ticket or had my board confiscated. If a law enforcement officer asks you to leave the road you are on, leave. There's always tomorrow. The links above should allow you to join the aforementioned organizations. Finding practice hills is usually a bigger challenge then getting ready to ride.