Depends on where you are. Look at the coverage maps for most cell providers. East of the Rockies you have coverage almost everywhere. As you start getting out West you have vast areas of middle of no where land with no coverage. If you are on a freeway in the middle of no where, coverage will be a lot better. For example I-80 through Nevada has coverage all of it's length. But get off of I-80 in the middle of Nevada and you may drive for hours with no cell coverage. Yosemite Valley has cell coverage, but other remote areas of the park do not. Death Valley has coverage in the tourist areas in the valley, but going into and out of the park you got miles of no coverage.
