They use, exclusively, $1 coins in El Salvador in place of bills. You'll find bills on occasion, but only in tourist areas. I'd like to see more of them circulated in the US. They use them in vending machines for change and at prepay transit tickets at the station.
That's interesting about El Salvador, adopting U.S. Currency and U.S. Coinage as their Official Monetary Tool of Choice... Doesn't El Salvador mean The Savior in English...???