One good place to eat in Mexicali is at those tacos de cabeza and borrego stands near the old train station.
Plus, you can pretend you're a zombie when you go there. Mmm, brains.
Yeah, it's called the "Perrocarril", There's like 10-15 stands right next to eachother that sell the exact same thing. If you like tacos de cabeza, that's the place to go. The only thing that sucks, is that sometimes one dude will get mad if you ate at his competitor's stand instead of his. But, it's still worth it.