I ride with my kids ages 10 to 24. I am still alive after many miles on the road, hope to be for much longer. As I tell my kids we are basically playing on the road, its a dangerous place be alert, use a mirror and keep your ears open keep the mp3, ipods etc. for home. We tour and spend hours and hours on the road at lot of times its very quite no traffic and life is easy two abreast is fine safe and no concerns but when we hear a car its single file all the way. If it is safe we are to the right of the road if it is not I have been known to claim the whole lane, I try to make eye contact or a wave or somehow aknowledge their presence. More than once in my life I have gone off the road in a controlled manner to allow a car or cars to pass if it looks like it will be more than a few seconds before its safe to pass. On some roads the grade or curves make it unsafe to pass due to lack of shoulders etc. in which case claim the road but even then do it in single file. The goal is to have the cars behind you in front of you as fast a possible in a safe manner.
You do not win when you fight with cars, and our favorite is its better to pick gravel out of you body than your body out of the gravel.