Preheat oven to 350F. Cook pasta shells according to package directions; drain and set aside.
Cook ground beef in a skillet over medium heat, stiffing until beef is browned and crumbly; drain and return to skillet.
Stir in taco seasoning mix and water; bring to a boil, reduce heat, and simmer until thickened.
Stir in cream cheese until melted.
Pour half of enchilada sauce in a lightly greased 8-inch baking dish. Spoon beef mixture into pasta shells; place shells, filled side up, over sauce. Pour remaining sauce over shells; sprinkle with cheese.
Bake 25 to 30 minutes or until hot and bubbly. Top with salad mix, sour cream and tomatoes.