There are strong opinions here re: sidewalks. There's one small stretch of my commute that's just a lot easier on a sidewalk (going toward work), and the sidewalk is very wide, and it's legal, so I ride on the sidewalk for a bit each morning. Plenty of room for me and the peds, I feel safe, and it works for me. You just need to assess your situation and do what you think is best in each instance, assuming it's legal to do so. I'm generally of the opinion that it's safer to ride in the street, assuming that cars in your town are used to bikes on the road, as you're much more visible there. But there are times when that's not going to be the case.

Good luck with the commute!