A big part of commuting is finding the safest way to go. If a couple hundred feet on a sidewalk is safer, then go for it.

A big part of my commute is a bike path, and that path shares a sidewalk for a couple of blocks. I just slow down, give pedestrians the right of way (and the benefit of the doubt), and a couple of minutes later I'm through and on my speedy way again.

Just be careful not to get lulled into a sense of false security when you're on a path or sidewalk - remember that those pedestrians can do unpredictable things.