Acapulco Joe's -- Downtown Indy. I've been eating there for over 25 years, and while there have been some inconsistancies as of late, especially after their head cook passed away, it is still hands down the best mexican in town. The only places I've found that were better were in New Mexico.
My favorite place was Queso Blanco in Westfield, but they got closed down. Not sure on the details, but I wouldn't be surprised if the closing was rooted in local politics. I've heard second hand reports of several of the downtown businesses taking crap from our local politicians. The 'Currents' newspaper stated that a business could lose it's license because they don't pay taxes. This type of reporting pisses me off. They don't actually say that the restaurant didn't pay their taxes, they just insinuate that they didn't. No facts, just insinuation. I don't know one way or another what happened, as there has been nothing announced officially by either the city or the restaurant owner. Shoddy reporting.
I remembered this thread from yyy back so I thought I'd put in a plug for my new favorite eatery, Los Primos in Goshen. Very small, mom and pop kinda place. Try the cabeza, mmm good. $1.50 tacos, I get 4 and can barely walk to the car. They pretty much Habla Americano, and I kinda speak Messican so communication is no problem. My kids are both in Spanish I this year so it's a blast to take them and make 'em practice. Oh, and ZX Guns is only a few blocks away.