I assume you're kidding, Diane. When I was there (several years ago) their prices made gas in Canada look cheap. It does sound like an almost plausible excuse for a good road trip...
Actually Brian, the gas prices in Mexico are now cheaper---somewhere around $2.50 a gallon. (varies some with the exchange rate--right now, about 7.43 pesos a liter) And, for anyone who needs diesel, it is about $1.77. Now, on the border, the prices went higher because the prices on this side were so high.
Yes, for years we just didn't pay attention to the gas prices in Mexico and just filled up the tank with a blind eye, because gas was a lot more expensive, but not now!
For us, almost anything makes a plausible excuse for a road trip.