CUSTOMS AND VEHICLES
Importing Household Goods and Personal Effects
Foreigners wanting to import household goods and personal effects must first apply for a Temporal Visa from their home country. They then have 6 months to import their goods tax free after the date of entry into Mexico. The goods must be at least 6 months old and must be accompanied with a detailed inventory list in English and Spanish citing serial numbers when applicable. For more detailed information regard customs regulations see below:
http://webportal.atlasintl.com/Customs%20Docs/mexico.pdf
(Hold down CTRL key and tap the link above)
Importing Foreign Plated Cars
Foreigners entering Mexico under a Tourist Visa may bring in a foreign plated car for a maximum of 6 months. You will need to buy auto insurance at the border, or on-line in advance of coming across the border.
For Temporal or Permanente Visa Holders there are very specific rules and regulations as details at the in the website below:

Bringing Foreign-Plated Cars Into Mexico


Foreigners with a Tourist Visa cannot purchase a Mexican plated car. They must have a Temporal or Permanente Visa to own a Mexican plated car.