US citizens should have a passport that's valid upon their arrival in Mexico. Irish citizens should have a passport that's valid upon their arrival in Mexico. Australian citizens should have a passport that's valid upon their arrival in Mexico. ESTA applications could be submitted at any time prior to go to the United States of america, and VWP travelers are encouraged to make an application for authorization whenever they start to plan a visit to the usa. Visitors from certain countries do not want a visa as a way to enter Mexico. Overstaying your permit will cause mandatory fines that you will need to pay as a way to leave Mexico.