Using your card is the best way, unless you have a Mexican bank already.
There are plenty of ATM,s the closest is in the mini shopping zone next to The Riu Tequila. I use the banks in the Centro Maya shopping plaza across the highway 307. there is at least 2 ATM's in Bancomer and Scotiabank.
Word of warning check your card issuer for hidden charges, my bank Barclays charged me £4.60 commision on each 3000 peso withdrawal. They also charged me commission for using my card for buying any goods, worst charge was £35. (it was a fairly big purchase)
Think Nationwide is still free from charges.