There is a relatively new Mexican place on Mamaroneck Ave. I noticed it about two weeks ago and tried it today for lunch. I really am not qualified to say how authentic it truly is, however it seemed like the real deal to me. I went with a friend who had been there before and apparently they didn't have anybody who spoke English when he first went.
As you enter, on the right is a counter with maybe 8 seats and then on the left are maybe 6 tables that each seat four. There was a lady with a little kid in the back corner; she seemed to know the one waitress.
The guac was good. For my main dish I had a carne burrito, which I liked quite a bit. It came with rice and beans on the side. Again, I really can't comment on how authentic it truly is. They had a ton of stuff on the menu that I had no idea what it was. Two things that caught my attention were something with tongue and a chicken dish with a Mexican chocolate sauce.
Some of you are probably familiar with Juarez Grocery on Mamaroneck Ave. I've seen posts here talking about the tamales that they have on Sunday mornings. I have no idea if the restaurant is related to the grocery store.
As for price - the burrito was $7 and the guacamole was $2 and it was filling enough that it was the only thing I've eaten today aside from a peach and a banana.