Maybe, but you need to send the balloon to that place and inflate it, then you need to control its altitude so people could get signal on the ground. It doesn't seem to be easy.
An UAV's advantage is that it can fly on its own and fly a long distance (Wing Loong's flight time is said to be 30 hours). Given enough drones they can deploy a continuous mobile network across a large area.
One good alternative I can think of is deploying small self-contained mesh networking devices, something like Project Owl, directly from air. These devices can form an emergency network for communicating urgent needs.
