Renewing your US Passport
You can only renew you passport at the US consulate serving the area where you live in México. You must appear in person.
This website is for renewing by mail, which you cannot do from México, but it contains useful information and will lead you to the application form which you will need to fill out and take to the consulate. Use the option for filling out the form on line; it is easy and works well, Form DS-82
You need to contact your consulate to find out their hours and local rules. Here is a list of consulates with links to their websites:
If you live near México City, you can go to the Embassy.