Ideally, you wouldn't want EVERYONE to be trying to communicate at once during an area-wide emergency. Let the communicators do the communicating, and get the message to another party who can let everyone else know what to do and where to go. Let's see, what type of service could reliably do that???
BROADCAST RADIO, particularly a LOCAL live-staffed AM radio station. No one wants to lug around a TV set for emergency information, so forget them. Most FM stations in California (and the rest of the US for that matter) are automated music stations with no one actually live-on-duty, so forget them also. Cellular phone service in most cases will be DOA. Find a local AM station, make a plan that includes them, and tell EVERYONE that in times of emergency, they need to grab a portable AM radio, and tune to whatever frequency to get continuous updates on the emergency. The local hams and GMRS operators, as well as first responders and government officials can all be in contact with the radio station to give them updates, and they will tell everyone else... many times with live on-the-scene audio actualities.
That local AM radio station has between 1,000 and 50,000 Watts of transmitter power with backup. You don't. They have hundreds of miles of relatively high-fidelity audio coverage. You don't. Between emergency updates, they can tell the audience where to find help, and keep them calm with a few music selections. You can't.
If you know how to use a 2-way radio, then great, but most people only need the radio that they are most familiar with. Broadcast. Just let them know in advance what station to tune into if there were to be a local emergency.