Yeah that's a fair point. You probably[1] need to be online to make a transaction, but you can potentially have a thin client setup where you communicate with a hosted node somewhere, but the signing and stuff is kept on-device. This allows you to make transactions in the case where power is out, but your phone still has internet access. I don't live in el salvador so I'm not sure what the frequency of power outages is relative to telecommunications outages, but at least in the US cell towers and landlines run on backup power so they're up even when there's a blackout.
[1] For maximum convenience it's mandatory, but it's conceivable to update the state of a channel entirely offline. This would allow you to make offline transactions with a node you have a direct channel to, but multi hop transactions (ie. transactions with nodes that you don't have a direct channel to) would still be a hassle.
