having cell service is a good idea. you can either set that up with your current provider or you can get a local sim for cheap. if you do neither, id highly recommend downloading the map of the areas you are going on google maps, because gps works even without cell service. 

also, if you are needing driving directions, i highly recommend using waze over google maps. google maps has better maps to look at, but waze navigation is much better. google maps navigation has literally taken me to the bank of a river expecting me to cross it.