Having just returned from a wonderful vacation in the South of France and Barcelona (driving between Barcelona & Nice), I thought I would share some observations that may be helpful to some, i.e.:
1) The tolls on the Spanish Autopista AP-7 in Catalonia and French Autoroute A9 in S/W France had no trouble accepting our Visa credit card, which has the "new" tag on it that they apparently require. However, the French Autoroute A8 did not recognize ANY of our credit cards (all Visa) and as such we had to scramble for Euros. It was not a credit card issue; they worked fine, subsequently, in our hotels and parking garages.
2) We rented a car from EuropCar at the Barcelona airport. We arrived at their booth at 6:30AM and found that they were closed. An attendant at the neighboring Sixt booth, which we were told was open 24X7, said that EuropCar doesn't open 'till 7AM, so the wait wasn't that bad. However, we were not told this in advance by EuropCar when booking the car.
3) The EuropCar GPS was awful. It worked fine in Spain, but we were only there (in Catalonia) for a relatively short part of our trip. When we configured it for France and tried to use it, it would not recognize any location. The map showed no details, either, in France. (As such, we are pursuing a refund for the GPS.)
4) The GPS would've come in handy in, specifically, the region around L'Isle sur la Sorgue & Avignon, Cannes and Monaco. We found road signs there to be particularly wanting. Route numbers are not prominently displayed, if at all. Often a town name or other landmark would suddenly no longer be displayed at a junction, causing one to rely on instinct and guesswork. Even critical junctions leading onto Autoroutes did not have signs at entrance ramps to reinforce which direction it would take us to, causing us to go many miles out of our way via backtracking (an extreme case happened near Arles when trying to go west on the N113 from D570N).
5) Based on the above, we learned to avoid back roads. Though they can be fun, unless you can afford the time to get lost, it's better to take Autoroutes and other primary roads if you are looking to get someplace in a reasonable amount of time.
6) Probably obvious to most everyone that's been to Europe, but you should avoid renting anything larger than, say, a VW Golf (the car we had) if you are going to cities. We were grateful to have a relatively small call when finding ourselves driving through, as an example, L'Isle sur la Sorgue (after market hours) and in the underground parking garages. The latter typically have very tight spots and extremely narrow ramp clearances.
7) Take the train to Monaco. We didn't, and regretted it. Particularly w/o a working GPS, it was a huge challenge to find anything. Though the train station is a long way from sights such as the old city, aquarium, famous church, etc., better to walk it or take a cab from the train. If you must drive, make sure your GPS works or you've mapped out your route to a "T".
8) The memorable stops on our trip were the markets in Nice (Monday) and L'Isle sur la Sorgue (Easter Sunday); Eze; the aquarium in Monaco; Roussillon; and the Chagall Museum in Nice.
9) We also enjoyed the Rothschild house & gardens just east of Nice; a stroll on Cannes' Rue Meynadier with its shops and cafes; the fascinating (though crowded) Avignon; a pleasant dusk stroll through a still-open Sunday market in Pezanas; the somewhat spectacular still-standing Pont du Gard (despite the tourist trappings); narrow corridors of El Borne in Barcelona and much more.
Cheers,
Bruce Kanin