I'm an aspiring future tesla owner... i live in an area with very patchy 3G coverage, and I'm wondering how this will effect the operation of the nav and other functions. Particularly the maps - if there is no 3G signal, is there no map displayed? Is it possible to cache maps using wifi before leaving home, if one anticipates a poor connection during the journey? Just wondering how reliant on a constant connection the system is... Thank you!