Combine cream cheese, sugar and margarine, mixing until well blended. Beat in banana and eggs. Add remaining ingredients except nuts and (optional) blueberries, mixing just until moistened. Fold in nuts and blueberries (if used). Pour into greased 9x5-inch loaf pan. Bake at 350 F for 1 hour and 10 minutes or until wooden pick inserted near center comes out clean. Do not overbake! Cool and then remove from pan. Cut into slices and store in an airtight container.