As I get on in years, it occurs more and more often that I go around the roundabouts a second or sometimes even a third time. However, I have noticed that it isn't always my fault (although it usually is). Sometimes the necessary sign is missing for one reason or another.

A former poster used to complain about the "absurd" practice of driving with the headlights on during the day in Europe and also whined about the left and right lane thing. I think they are dead now.

I almost never use the left lane except when passing a tractor.

Are there any places appropriate (or inappropriate) for on the road picnics?

Bien Sur! Autoroutes have aires de repose (sp?) with outdoor tables. Regular roads are really busy but take a side road and you'll find many neat picnic places - we always did so but respect property rights.

This is not specifically French, but you may encounter "Zones" in France or elsewhere in Europe.
The most common could be the "Zone 30" , typically in residential neighborhoods or historic city centers - with the respective traffic sign for 30kph and the word ZONE.
It means that anywhere beyond that sign, also on crossroads etc., the max speed will be 30kph - without any further sign reminding you.
Until you see the same sign "x-ed" out.

The main comment my French friends say about French drivers is that they are so inpatient.

What I remember most is being careful on the autoroutes to stay out of the way of fast cars coming up behind with a great degree of impatience. Do NOT drive in the fast lane unless you are passing, and then move over as soon as it is safe!