CA – Indian Cove Nature Trailhead 0.5 miles hike (Joshua Tree) – ATT Verizon 3 bars T-mobile 1 bars

https://maps.app.goo.gl/5N2bkatZMhJDmedy5?g_st=com.google.maps.preview.copy

This trailhead is outside of the NP. So it is free. Good phone services to do work. A very short hike (0.5 mile).