Cave Springs? Not ringing a bell and I thought I’d been everywhere. But 89A north is doable though I wouldn’t suggest taking it from Sedona to Flagstaff with a big rig. That was one of my favorite roads when I rode motorcycles because of the grades and tight curves. Some people claim to do it but I can’t believe they manage to stay in their own lane and they likely acquire a trail of hostile solo drivers, especially going uphill.Your phone should work OK, again the only questionable area might be the Sedona-Flagstaff stretch which is somewhat less than 30 miles.
After posting I realized that route takes you over Mingus Mountain and through Jerome, an emphatic no for a big rig.Sorry for the sloppiness.
