If SHTF, one of the very first things to be shut down is cell phone service. If you think you can rely on your cell phone to work in a disaster, think again. In a crisis, everyone reaches for their phone. Cell sites can only handle about 150 to 200 calls per second per sector. Anything more than that and they just start generating busy signals. The network can't handle a sudden surge of calls at the same time. Also, the networks can be switched to "emergency calls only". If SHTF and you can't call on your cell phone (which will probably happen)... try sending a simple word text. NO emoji's, no graphics, no photos... just simple text. Cell phone towers treat that differently and handle it as a small byte data transfer. A simple text will often go through when a cell phone call is impossible.

One excellent solution that will work for neighborhoods, nearby relatives, etc... is to go online to Amazon, Walmart.com, etc... and order a set of LONG RANGE ADULT WALKIE TALKIES. Many of the models only cost about $60 for 3 Long Range walkie talkies, or right around that price range. You can get 4 for about $80.
In a rural area, you can get 10 miles of range on a lot of the models. In the suburbs and neighborhoods, you can expect to get 2 to 3 miles of range. In a city, it may only be 1/2 mile to 1 mile range. Still, that's enough to keep in voice contact with grandma or your other relatives. :>) You can all keep tabs on each other, hear each other's voices and trade information even if cell phones are completely shut down.

In a neighborhood situation, if you needed to organize things with the few neighbors who are reliable... maybe 4 or 6 walkie talkies would help coordinate happenings in the neighborhood or you could alert each other to things. It's also a great way to protect your neighborhood.

It's a really small investment and you can get them in 2-days or so. It might make a world of difference if needed. Just pre-plan what channel everyone will be on and practice beforehand to make sure everyone is on board.