Preheat oven to 350º. In a large bowl, stir together cream cheese, mayo, sour cream, garlic powder, most of cooked bacon (reserve some for topping), most of the jalapeños (reserve some for topping), and 1 cup cheddar, and 1 cup Monterey Jack and season with salt and pepper.
Transfer to a oven safe dish for baking and sprinkle with remaining 1/2 cups cheddar and Monterey Jack, bacon, and jalapeños.
Bake until bubbly, 15 minutes, then broil for 3 minutes