Realize that sidewalks hold dangers for bikes and might not be the safer option. When on sidewalk you become basically invisible to car drivers who are looking for vehicles on the road. Come to an intersection expect that cars will be turning in front of you. Same at driveways. Kids, dogs, leashes, joggers, trash cans, other stuff on sidewalks. If riding on sidewalk should limit speed to like 10 MPH or less (depends so much on where you are). On the road you have other issues, but can move along as fast as you can peddle most times.

Some good tips on commuting on bike in this link (suggested reading):Bicycle Commuting