I know a lot of "those people" who are using Bitcoin already, but I would never refer to unbanked people as "those people," being for all practical purposes one of them. We mostly aren't using it safely (a lot of us don't know the difference between Binance and Bitcoin) but we are using it.

The last transaction fee I paid was 33¢, and the average transaction in the last Bitcoin block was 913 bytes, so your internet access speed isn't an obstacle to sending a transaction as long as it's above about 20 bits per second; if you want to run a full node you need at least 17000 bits per second of internet access unless you're using the Blockstream satellite.

Typically I pay US$5 a month for cellphone internet access when I have it, but more commonly I use Wi-Fi in various places.