CD are accepted some places but not all. USD are accepted in most places. Pesos everywhere. However do not exchange you money for pesos at home, at the airport or your hotel, but rather ate exchange houses (cambios) that are all over the place.
Most folks use the ATM machines for cash (only get pesos from the machines here) and usually at a very good rate. If you have a Scotia bank card you can use those Scotia ATMs here with no bank fees. However doo notify your home bank if you plan on using Credit cards or ATMs, or Debit cards or they will put a hold on the card with the first use fearing fraud.
Also remember if you $10 tourist card fee (when you land) and your $20 exit tax(when you leave) if not included in your travel package MUST be paid in USD.