Our group's experience is having no driving experience in Europe or racing. Those who didn't go over the roadway signs had trouble the first 2 days driving in town as they had to second guess the signs. That is why I recommended going over the roadway signs at a minimum to try and keep other traffic moving. The US military will issue drivers liscenses but as to what they apply I have no idea and they may or may not issue them to spouses. I am not in the military so I have no idea.
As to using a normal US state drivers liscense in the Europe, I am speaking on purely legal ground. What the local constable does is up to him. The European Union or other foreign governments are not under any obligation to recognize a US state's drivers liscense as they are not issued under the US sovereignty. They are issued under the state sovereignty ie. California, Arizona et al. There is no formal treaty that I am readily aware of that will acknowledge a US license as equal to the local license. I believe that the local governments overlook this fact to not clog up the court systems with Americans driving without local licenses and get along with the US Government. There is, as I understand, a treaty governing International Drivers Licenses, thus the International bit. When the Mexican cop pulls you over and asks you for a Mexican license, he actually does have a legitimate right to ask for that document. If he takes $50 to look the other way, that's his perogative.
The permit issue is one that we have dealt with on renting cars here in Europe. The Avis at Frankfurt airport has asked for them the 2 times I've been present at the counter. They cared little for the US license if there was no permit. They might do it for regular customers or the frequent renters but according to their company policy, they want to see it. Plus, it's $24 that hopefully will never have to be used.
I will admit that maps that are easily read by one person are not read easily by another. I am not recommending buying a hand held GPS unit, only getting a car with the navigation. For those who have never been to Europe, it definatly helps. Again, this has been our group's experience. By the way, what map "brand" have you found to work better than others? At least it's another recommendation and thanks for the input.