Riding on sidewalks is legal, except in 'business districts' and where prohibited by statute.

I've seen some cyclists switching from road to sidewalk and back within a block, for no reason that I could see. (No obvious undodgeable holes or patch mess in the road, no impending flattening of the cyclist, no big clots of pedestrians on the sidewalk.) One I remember appeared to be taking either green lights or walk signals, whichever were more convenient to him. I have no problem with cyclists on sidewalks as long as they behave like pedestrians. I have no problem with them in the street as long as they behave like cars. I just want them to pick one and stay with it.