Hi Richard,
I am sure Henry will respond to you in detail ... but just a quick comment from me regarding currency .... Anywhere in the world (does not matter South America/Europe/Asia) if you use the local currency you lower the risk of getting ripped off by the store owners (like we do it everywhere!!!). I highly recommend you to buy your foreign currency here in Canada and have some USD cash as a back up (you never know you may find a nice airplane model or something there
and of course your CC. However, again by experience, do not allow your plastic to be taken to another room to be charged especially with a manual machine ... use it where ever it is an automatic CC machine. I wish I were able to go to Argentina & Uruguay! Argentina is amazing, Uruguay is cute ... Lots of good food, wine, beer, beaches and sightseeing
Have fun & make sure to prepare a "TRIP REPORT" we'd love to hear
Idil