Preheat oven to 350°F. For crust, stir together flour and brown sugar. Cut in butter until mixture resembles coarse crumbs. Press crumb mixture into the bottom of an ungreased 13x9x2-inch baking pan. Bake in preheated oven for 15 minutes.
Sprinkle pecans and coconut over partially baked crust. Combine sweetened condensed milk and vanilla; pour over crust. Bake at 350°F for 25 to 30 minutes more or until filling is set. Cool in pan on a wire rack for 10 minutes.
In a small saucepan combine caramels and milk. Cook and stir over medium-low heat just until caramels melt. Drizzle caramel mixture over baked filling. Sprinkle top with chocolate. Cool completely. Cut into bars.