Yet while many prescription drugs in the U.S. are sold over the counter in Mexico, you still may need to show a prescription for them at U.S. customs (like Valium and Xanax.) Here is the U.S. Consulate's official position on buying prescriptions in Mexico. This line really stood out for us:
The sentence for possession of a controlled substance runs from ten months to fifteen years in a Mexican prison.
That said, people are buying prescriptions meds in Mexico all the time. We're not sure all the tequila in Jalisco would convince us to do it.