AT&T or T-Mobile Tourist Plan for CA Coast

Verizon is pretty solid on the Calif coast. Never had a problem. Someone mentioned hiway 1, it's now open.

I just spend about a month along the CA coast and the T-Mobile service was terrible. Luckily I also have AT&T for data service and that was usable but the signal strengths pretty low. I have been in those same areas in the past with Verizon and have had no problems. I just had to drop Verizon due to the high cost and low limits on their unlimited data plans.
I am pretty sure that both T-Mobile and AT&T would have benefited dramatically from an external cellular antenna.

Check with CA DOT on highway 1 between Monterey and San Luis Obispo. It was permanently closed to through traffic not to long ago. Another vote for Verizon we have verizon and t-mobile phones the verizon is almost always connected t mobile not so much out of towns.

We camp a lot on the WA and OR coast. T-Mobile was very spotty or worthless. Verizon always solid...

Sorry, can't speak to CA. Haven't camped there for a few years.

Verizon would be your best choice. ATT a close second. All the others a distant third.

Good luck finding any cell service whatsoever south of Pfiffers SP to about Pideras Blancas. None at Kirk or Plaskett Creek USFS for instance.