For the most part this works surprisingly well, as demonstrated by the Cajun Navy. The occasional dropped packet just means a short gap in voice. Text messages can be retried automatically.

So the real question you have to look at for your area is: Will the cell towers be overloaded, or will your Internet go away entirely? If the former, you can probably still use Zello. If the latter, you'd better have some other options in mind. [3/5]