I got all of the following off of a Baja website. Some of this is news to me. These changes were suppose to have been made September 2015. Can anyone confirm?
1. An FMM is required even in the free boarder area, including all of Baja, assuming you are a non-citizen/non visa holder.
2. An FMM for less than 1 week is free, 8-180 days is $533MXN.
3. You can get them online ahead of time, but still have to stop at the border INM to have it stamped if you enter Mexico by land.
4. You can enter/exit Mexico repeatedly during the time your FMM is valid.
5. You no longer have to surrender your FMM when leaving the country. You use it until it expires.