Here's my answer. Note how limited your alternatives are when the communications systems that we have come to depend on don't work.
- HAM radio. Time and again, when there is a major disaster, HAM radio usually becomes the only way to communicate. I highly recommend that everyone become certified, at least at the most basic technician level, to use a HAM radio and then go out and buy a basic radio.
- Computer/internet. If you have power to your computer (a laptop with a battery or a generator), and to your modem/router there is a possibility that your internet provider will have a back-up battery system which will allow them to continue to provide internet service as long as the battery holds out.
- 2-way FRS radios. These are the radios that you can buy in a set at Walmart that have a short one to two mile range. Families often use these for communications when they are on vacation out in the woods, on a cruise ship, or other places where regular cell service isn't available.
- Cell phone/texting. Even when the power is out, your cell phone may still work. Most cell towers have some sort of battery back-up so that the tower can still work, at least for a few hours after power has been lost. Note that if cell circuits are overloaded, as they probably will be right after a disaster, you may still be able to send a text message through.
- Your own two feet. I was recently invited to observe a full scale disaster exercise at a large company. The scenario was an earthquake which took out all power and communications among other things. As soon as the exercise started, the phones in the EOC (Emergency Operations Center) started ringing off the hook. People in the EOC would pick up the phone and say "this is a drill, the phones are not working". The people on the other end of the line would then ask how they were supposed to communicate with the EOC if they couldn't call. Simple, the Emergency Management Team members would say, send a runner to the EOC with your information. It hadn't dawned on most of the people in this large complex of buildings that should the power go out and if they didn't have radios, they will be literally walking to get the things/news/information they need.
- Written messages. Long before cell phones, and even before CBs became popular, our preferred method of communicating with people that we had plans to meet with up in the mountains were simple signs, written with a black marker on a white paper plate, tacked to a tree. If you have no power and no services and no communications for an extended period of time, that may need to be an option for you too. Basic signs can be pre-staged in your home. Messages can range from OK to NEED HELP to NEED WATER, or other messages that you are likely to use during a disaster. The bigger the letters and the more contrast in the color, the easier it will be for others to see.
In an emergency, you can send a runner, or run yourself, to the local fire department/police department/hospital/road department office/other critical infrastructure location which is likely to have emergency communications equipment. Remember, however, that these agencies really do not want to see people flooding their location during a disaster. They will be busy mounting their own emergency response and unless it is literally a life or death situation, your needs will pale in comparison to that of the community at large, so only do this in a dire emergency.