According to both the Hertz Rental Car agency at Newark Airport and a call to the NJ MVC I do need an international driving permit in addition to my German license when driving in New Jersey. However, according to two local tourist agencies in Germany and most importantly the website of the NJ MVC, http://www.state.nj.us/mvc/Licenses/Visitors.htm , I do not need but am only advised to have one.
Does anyone know where to get reliable information on this? Maybe even a listing for all states, so when I'm driving around on trips I don't have to go through this for each of the 20 or so east coast states again?