I've gotten counterfeit change at the club where you pay to leave your coat. Then again i think that they didn't even know it was counterfeit since the flow of money is just fast. ATMs i would have to say it something not confirmed.
I know a local who works in the corporate offices of a major bank. She only gets her dollars from her bank. (Changing pesos to dollars to hold until she needs to change them back to pesos.) When she took in some US$100 bills to change at her own bank, they said that one of the bills was counterfeit and they took it and she was/is s.o.l.
So if they are selling and then confiscating real/counterfeit US dollars, it's probably also occasionally happening with pesos as well.
It never happened to me, a couple of friends of mine told me they got fakes from an ATM but then when I asked them what happened they said they took money out, took a cab then paid with 100 pesos bills and the taxi driver obviously changed their bills like they usually do when they claim they can't take your money cause it's fake
I don't know about the fake bills, but i have definitely been under changed at an ATM. I withdrew $700 pesos at the HSBC in the Ezieza airport, and the machine gave me 5 $100 notes and 2 $2 note. Thats $504 pesos, but my receipt says $700 plus the 11.25 fee. I didn't notice till i was already in a cab. Be careful with those ATMs.