We were able to successfully use our credit cards at ALL Pemex stations on the way to Zihuatanejo this year. We prefer to use our cards so that we don't have to carry that much cash, and our cards are 1.5% cash back cards. It adds up.
We use Capital One because there are no fees of any kind when used internationally. Check the archives for loads of information on this.
We live using our credit cards almost exclusively, all over the world. Sometimes things happen, we feel it's random, as do the card issuers. If you are worried, carry more than one, like we do!
Remember: Relax, have a great time, and enjoy yourselves!