Cook the pasta according to package directions. Be careful not to overcook.
While the pasta is cooking, in a small saucepan over medium heat, combine the next five ingredients (evaporated milk through garlic salt). Whisk and cook for 2 minutes, or until the mixture comes to a low boil and thickens. Turn off the heat, and stir in 1 cup of cheese. When smooth, stir in the green chiles.
Drain the cooked pasta, leaving it just slightly wet, and add it back to the pot. Immediately stir in the cheese sauce and last 1/2 cup of cheese, and stir well until the pasta is creamy and well coated.