Hi Cathy,
The national currency of Mexico is the New Peso. You can take Mexican Pesos and if these are not available at your local bank then Euros or US$ are widely accepted. Euros are preferred to £ Sterling, which is becoming increasingly difficult to exchange. Please be aware that an exchange fee will be charged to change the currency to Pesos.
There is an extensive network of ATM’s around the country, but they only dispense the local currency NOT US$. Credit cards are normally accepted at the larger hotels and shops. It is recommended that you contact your bank prior to departing the UK to inform them that you may be using your credit or debit card whilst you are away.
Kindest regards,
Monty