A little while back, the California Association of Bicycling Organizations people discussed this article in The Inland Daily Bulletin in which columnist Michelle Pearl asks the local CHP for the Final Word on traffic law for cyclists. A retired police officer "took umbrage" at an earlier statement about the legality of riding side by side on California roads, so the CHP asked Pearl to "run a correction" that turns out to contain patently untrue information.
On the CABO list, Dan Gutierrez and others highlighted what California Vehicle Code says about bicycling on public roads. LA Streetsblog published Dan's excellent analysis of California law as it relates to Pearl's column shortly afterwards. He also addresses the status of discriminatory laws that apply distinctly to bicycles but no other slow moving vehicles.
In spite of what the law clearly states, however, "be prepared," as San Diego Bike Coalition board member Jim Baross writes, "to hear otherwise from your friendly cop on the street. It is not a good idea to try to argue on the spot with police folks. Take notes and deal later with a superior officer if possible."