A good rule of thumb is if the price is listed in $J pay with $J, if it's listed in $US pay in $US. This way you avoid conversion hassles. We always bring travelers checks and convert to $J. We also bring $US cash for tips and odds and ends. We do use credit cards for expensive meals and for our room. You can also use your credit/cash card at ATMs just be sure to alert your bank or card issuer that you are traveling so they don't deny the charge.
