You have the right to import a used vehicle, with a minimum age of eight to nine years, even if it is not listed in the Register of importers. The process can be made by the following channels:
Some relative or person of trust, whom you have authorized by power of attorney (a public document authorized by a notary public that allows you to appoint another person as your representative so he/she can act on your behalf), must go with a real estate broker for selling, or keeping, the property. In case there is a mortgage involved, when re-entering Mexico the necessary arrangements must be made in order to continue covering payments through bank transfers.
Blank Power of Attorney forms are available here.