If you have a Triple A (American Automobile Association) membership, they apparently will rescue you if your bike breaks down.
If you are really worried, plan your route in loops around your home base, so that you are never too far away. And, as others have recommended, carry some cash. Though, in the event of a serious breakdown, you might not need it - strangers are often remarkably helpful -- I've been offered rides home even when I have merely been fixing a puncture on the roadside.