The Mexican government(s), in its'/their infinite wisdom, prohibits the sale of alcohol during elections and July 5th, when there will be elections for diputados (a political sub-species of popular representative that makes a huge salary and does precious little for those he or she is supposed to represent) is no exception.
The all-caring government doesn't want the nasty populace having the opportunity to buy a beer on election day, in case it gets drunk and votes incorrectly. Or gets drunk and disorderly if the election results turn out not quite the aforementioned populace wants.
IMHO, a ridiculous and useless law since those who will want to be drinking during the voting process will have bought their alcohol prior to the cutoff date, July 4th.
It's all part of the great simulation that we live in a "democracy". Call me a cynic. My wife does. :)