There is usually good cell service at both Cliff Dwellers Lodge and the South Rim. Beyond that, don’t count on it. You aren’t likely to get good service until after you’ve left Bar 10 Ranch. Trust us, once you’re in the canyon, you’ll be glad your experience can’t be interrupted by phone calls, messages, or emails.
We don’t recommend bringing your phone at all, but we understand that some people want to have them handy upon return or to take photos and will take a chance with them on the river. If you do this, be sure you understand the risks of exposing your device to water and fine sand. Make sure your device is waterproof or in a good waterproof case/bag in the middle of your night duffel and be careful. The elements can be unkind to electronics in the canyon.