Preheat oven to 400 degrees F. Lightly oil a 9x13 baking dish; set aside.
Heat 1 tablespoon olive oil in a large saute pan over medium high heat. Add onions and garlic and cook until softened, about 3 minutes. Add beef and taco seasoning and cook until beef is no longer pink, about 3-5 minutes. Stir in salsa and bring to a simmer, then add the cream cheese, 1/4 cup cheddar cheese and 1/4 cup grated Monterey Jack cheese and stir until completely melted and combined.
Spoon 1/2 cup enchilada sauce into bottom of prepared baking dish. Stuff shells with the beef and cheese mixture and arrange in the dish, keeping the shells close together. Drizzle the remaining 1/2 cup enchilada sauce over the shells and top with remaining 1 cup grated cheddar cheese and 1 cup grated Monterey Jack cheese.
Bake 20 minutes until cheese is melted and sauce is bubbling. Top with pico de gallo and cilantro leaves for garnish.