If you're at the Mandalay Bay Beach and pool, check out Border Grill for some fresh eats.
I was most impressed by the way they make their tortilla chips - I haven't had anything like this since Mexico! The drinks are eclectic and the food is gourmet, fresh and healthy. I vegetarian-ized the turkey tostado salad and it was yummy, as were the sweet corn tamales.
No blown mind experience here but definitely a nice lunch.