Hopefully someone taking a tour trip would know enough to install the maps locally on their phone, an option on many phones if your carrier has not neutered the Android OS.
For those who don't know: Zoom to cover your desired area, then in search bar type "OK Maps" without quotes. It will cache everything visible for your use later. It also caches a few zoom levels down for you so you get a lot of detail.
Google maps on a Android device IS a proper turn by turn GPS app that does not need towers and uses built in GPS receivers in the phone. The towers are only used to refine your position faster, so even without them it is equal to a GPS only unit, with the towers its more accurate than any standalone GPS, including military devices.
Good phones like the Nexus 4 or 5, the new Samsung phones, or as much as I hate to say it iphone 5 or newer, can do nearly everything a arsenal of mobile products + a laptop of a few years ago could do, and they do it better with longer battery life. The only draw back I have found is the inability to use certain phone touch screens with gloves on.