I wish Thomas Cook, First Choice etc. would stop telling people this. It's false and they are just trying to fill their own pockets. The truth of the matter is that Mexican banks have made it more difficult for individuals and companies to bank US Dollars in an effort to reduce the amount of drug money from being laundered - there is now a monthly limit in place on the number of dollars you can pay into a bank account or exchange. This doesn't affect the tourist in any appreciable way, but it does affect travel agencies such as Thomas Cook. Before, they would take dollars as payment for their already overpriced tours, but now they have trouble banking them. By telling people Dollars are no longer accepted in Mexico they hope Brits will bring Pesos or Pounds instead and therefore reduce the number of people who cant pay for their tours because they brought Dollars with them. As mentioned by others above, Dollars are still perfectly acceptable for almost all purchases in the Hotel Zone and there are even cash machines that dispense them directly. So much for 'no longer being accepted'! That said I would always advise anyone (Brits especially) to bring Pesos over Dollars as you'll suffer from far fewer rip offs on the exchange rate - just don't use them buy tours from First Choice or Thomas Cook!
