Do you have much experience cycling in traffic? I'm asking because it can be pretty daunting the first few times. There's a lot of stuff going on, vehicles aren't too patient (especially around rush hour), and it's easy to feel overwhelmed.
I have been riding 12 miles each way to work for several years now. There are about 100 ft of bike lane on that trip, and about half the distance is in very busy city traffic. Taking the lane when necessary, signalling your intent, and figuring out how bikes fit into the flow of traffic radically reduces the risks that you're focusing on. There are risks to cycling, but I honestly believe that they're overblown. If you have particular concerns about part of your route, send me a google maps link and I'll see if I can help you plan out a better way to get where you need to go, or if I can offer suggestions regarding particular turns or sections that feel dangerous.
As far as stretching . . . just stretch after your ride for a couple minutes. You can toss a leg up onto the bike rack, a nearby bench, or whatever you've gotta do. At least initially (while you're getting a feel for vehicular cycling) you shouldn't be going much harder than you would while out walking, so I'm assuming that the need to stretch should be reduced somewhat.
