Preheat Oven: Preheat to 350ºF.
Cook Bacon: In a large nonstick skillet over medium heat, cook bacon in batches until crispy, about 8 minutes. Drain on a paper towel–lined plate, then chop.
Mix Ingredients: In a large bowl, combine cream cheese, mayo, sour cream, garlic powder, most of the cooked bacon (reserve some for topping), most of the jalapeños (reserve some for topping), and 1 cup cheddar and 1 cup Monterey Jack. Season with salt and pepper.
Assemble: Transfer to a small ovenproof skillet or baking dish. Sprinkle with remaining 1/2 cup cheddar and ½ cup Monterey Jack, along with reserved bacon and jalapeños.
Bake: Bake until golden and bubbly, 15 to 20 minutes. If desired, broil for an additional 3 minutes to get the cheese extra golden.