My husband and I are a bit "quacky" when it comes to dining in the summer in Las Vegas -- we love to eat outside. The patio at "viva" (as we call it) is east facing, which means that by 6 pm, it's totally shaded. No misters, nothing fancy, but all to ourselves.
Might I recommend their fish tacos (get them crispy!), or their Camarones (we like the Ziuhuen sauce best, but the "mojo de ajo" is also delicious). If you're looking for bigger eats, try the Chicken Congac (O!M!G!).
Warning! This is NOT your typical burrito and taco restaurant. Oh, sure, you can order those things, but why would you? When you can have the mole enchilada (outstanding!) or the Chicken Congac (O!M!G!).
And don't forget the margaritas -- cadillac if you can!