Hussong's Cantina was a good place to grab a quick, cheap lunch while working at the Mandalay Bay Convention Center. It was especially cheap for me because the Foursquare deal was written incorrectly, so I had two appetizers for half off, and my total bill came to under $10.
I loved their chips and salsa, which were fresh and tasty. I thought the queso fundido was OK but not all that flavorful. However, I really liked the crisp taquitos, which were well-filled and good. Service was great and I'd return to try a margarita.