FMM's aren't free, cost about $28US each.
You pretty much have to get them at the border. At TJ, it's really easy with their new facility. Just follow MexicoWanderer's instructions above.
We always go in the nothing to declare line-we don't have anything to declare.
If you live in San Diego, just head to TJ for lunch and to hit an ATM and get your FMM's ahead of time so you don't have to stop at the border when you head south. That's what we do. We just park at the border on the US side and walk across.
IF you decide to do it that way, say so, and we'll walk you through walking to the right building.
