This has been discussed extensively in the Advocacy and Safety section. Look there to see what most people who respond - stay off the sidewalks.

One factor is that drivers who cross a sidewalk do not expect anything moving faster than a pedestrian to be crossing in front of them. I nearly hit a cyclist adjacent to the UNLV campus who was riding on the wrong side of the street, moving fast, and on the sidewalk. It is only by the grace of God that I didn't run him over because even though I had looked for peds, he came whipping across the street just as I was about to start out.