I ride on one sidewalk near home -- the roads nearby suck. My sidewalk route is about a block, and it isn't too busy with pedestrians. I got off and walk my bike if it feels too busy.
I ride about 5mph on the sidewalk, just a little faster than the pedestrians.
I hate when people go 10, 12, 15mph on sidewalks - as they are the walking area. You should go at walking speed.