Ahh! I live here in the Pacific Northwest; there is a crucial technology fact people are missing. It is all about the number of Cell Towers! Remember, this is a large area with a lot of ground to cover. Without cell towers there is nothing, no connection, nada. You may have the smartest, fastest smartphone out there - none of this matters if you don't have a cell tower in your area; you have no connection.
AT&T, Sprint, T-Mobile have poor coverage once you get away from the main cities and freeways. And a lot of the beauty is in the mountains, rivers, and ocean beaches. You run the risk of not having a connection in any of these great places. Go to the coverage maps of the major services and only one really stands out in cell tower coverage: That is Verizon.
So get an inexpensive Verizon phone and use it for voice calls. Use your IPhone to connect to a local coffee shop's WIFI and do your data there - like checking your email. I think IPHONE will do that? I use WebOS and never have any problems.