If you feel that riding the sidewalk is safer than riding the street at any point then there's no shame in catching the sidewalk. I've done it quite a few times. One thing I'm mindful of, though, is that pedestrians shouldn't be inconvenienced because I opted to ride. When I approach a pedestrian I dismount and walk my bike past the pedestrian. I know some might feel that's unnecessary, but I think of it as being common courtesy.

There's a difference between a sidewalk and a MUP.

I also have a commute that took me down some fairly busy roads. I used mapmyride.com to chart out an alternative route that allows me to ride roads the entire way. I spend most of my time riding through industrial areas before and after business hours (less traffic) and residential roads. The cool thing about mapmyride.com is that it keeps a running tally of distance, so you can adjust the route and see immediately how it effects distance - allowing you to tailor the ride to make the route as efficient as possible.

Good luck, be careful and enjoy the ride (and the benefits of riding)!