I was asking about cell service because I thought I'd use my phone's Google Maps (gps) to get me from Park City to whichever park I choose...and then back to Park City. I'm thinking that may kill too much battery life though and maybe I should just do it old school and write the directions down so as to save my battery life for when I get wedged in between a formation like James Franco and need one of you to save my life.
GPS (even on phones) does not need cell phone reception once you have the address looked up and put in. You will need a car charger though, GPS drains batteries pretty quick.