I have called DH at home from DL and had no problem. I have Cingular. The hard part is finding a quiet enough place to call. Even the bathrooms are loud! I talked to him while on the train - of course I turned off my cell just prior to entering the prehistoric grand canyon area Anyway, it should be okay.
We were just there a week and half ago and I also have verizon. We used the cell phones to communicate with each other and we have no problem with signals at all.