Cheap Mexican food is easy to find, but cheap sit-down Mexican is not so forthcoming. Luckily, Fajitas & 'Ritas in Downtown Crossing offers south-of-the-border eats with less cafeteria-style ambiance. Whether you're looking for appetizers and pitchers of margaritas or a full meal, there's plenty on the menu that will satisfy. The nachos are a great place to start, a huge platter of chips and cheese, starting at just $2.86. Choose your own toppings, like......