If you are a regular San Diego – Tijuana commuter you know there is little to none control by Mexican immigration officers when crossing from the US to Mexico (or the other way around). The reason is that if you are crossing the border from the US into Mexico, Mexican immigration assumes that you are either a US citizen or a US visa holder, which exempts you from a Mexican visa requirement.
Even though you may be exempted from a Mexican visa, you still need to get an immigration stamp on your passport showing the date that you entered Mexico and obtain an immigration document (FMM) that evidences your immigration status while in Mexico (e.g., tourist, business, other; FMM is the equivalent of US form I-94).
If you want to prepare ahead of time, you can obtain an FMM online when planning to stay in the border area (i.e., cities in the US-Mexico border).
FMMs may be valid for up to 180 days. Unfortunately, FMMs do not allow multiple entries; so before you leave Mexico you must hand it over to an immigration officer at one of the immigration checkpoints by foot, which means that, even if you are a Sentri holder, you need to walk through Mexican immigration (and US CBP). The downside of not handing your FMM back to immigration is that if you ever want to apply for a working permit or other immigration permit with resident status (e.g. temporary resident card) the Mexican immigration records will register that you did no exit Mexico (at least legally) and most likely will deny your application.
Check back here for our future post on different types of FMM and what you are allowed to do with them.