I'd love some advice please.
Will be travelling through Western USA for 2 weeks. I need a simcard (normal or iPhone 5) for mostly calling. SMS is not important, more incidental calling in case of trouble (911, roadside assistance, hotel, car rental and such). Thus we will not use it much hopefully. Data is not required also, unless there is a cheap package.
Thing is, we'll be travelling thru California, Arizona and Utah. I am concerned about coverage (Death Valley, Grand Canyon, other national parks and highways). If something could advise about the best carrier with good coverage there and where I can find more information about that one.
We can pick up the SIM preferably in LA(X) or NYC.

Also, is a SIM card available everywhere in the US (supermarkets) and do you need to activate it with passport or such?