This bitcoin transactions go cause issue with retailers and customers, imagine buying food of $10 at McDonald and your bitcoin transfer gas is $5 to make it faster because anything lesser fit make transaction last for hours meanwhile you don chop food... I hope they are working on fast mining process for quick confirmation of payments
Waiting I think about this is that they will be planning to help their citizens understand lightning network, also I believe say if their citizens understand what Bitcoin is, some will be making use of other cryptocurrencies which can make their transaction fast with low fee. About the lightning network, it is possible for a transaction fee of $0.00005 after a channel is opened already, with a transaction speed of less than 5 seconds or lesser. I see this as a means El Salvador will adopt the use of lightning network along.