For the dressing: Mix together the mayonnaise, milk, sour cream, parsley, cilantro, chili powder, cumin, hot sauce, garlic and salt and pepper to taste in a medium bowl. Set aside.
For the salad: Prepare a grill pan or grill for medium-high heat. Grill the corn until nice and golden, with good grill marks on the kernels, 10 to 12 minutes. Allow to cool a bit, then cut the kernels off the cobs.
Add all the salad ingredients to a bowl in layers: first the lettuce, followed by the tomatoes, corn, red onions, cheese and tortilla chips.
Pour the dressing into a small serving bowl and serve alongside the salad.