Regular where I live is about 7.20 Pesos per litre.
Lemme see, @3.8 litres to the gallon and 10.4 Pesos to the dollar........
That calculates out to about $2.63 USD per gallon.
Of course, if you get up closer to the border, the price goes up.
I guess Mexico doesn't want all those Gringos who live near the border to start crossing over to fill up.