One liter of alcohol and one case of beer may be imported per person every 30 days. No ID=no liquor. You must prove that you are 21 or older. If you show false or altered personal identification, the ID will be confiscated and you will be prosecuted.
People over the age of 18 may bring three liters of liquor or beer and up to six liters of wine. For more details, see our Mexican Customs section. What am I allowed to bring back to the U.S. from Mexico? Your personal belongings and $800 worth of purchased merchandise, duty free.