If you're nervous about being able to clip out without tipping over at stop signs, practice first on a trainer. You can practice clipping in and out all you want without the fear of embarrasement when you don't quite make it.

Also, most pedals have a tension adjustment that you can loosen it up to make it easier to get out of.

I actually found that at the beginning, it was harder to clip in than it was to clip out, so I had trouble starting, not stopping.