I get wary about riding around cars, too, especially when I haven't ridden for a while and I'm not feeling too confident about my unclipping skills. Start riding on a bike path (but scope it out first to make sure it's now crowded with ignorant people walking their dogs and taking up the whole lane). Then ride around your neighborhood. Then scope out a more rural area without as much traffic.

As you get more time in the saddle, you'll feel more confident and get ready to take on bigger challenges.