You can't script layout-actions, layout-work. Using 'textformat' functions, one can set textattributes for text in browse mode, but not in layout mode.
You can drag with the mouse to select all objects within a layout part (or control-drag/command-drag). 'select all' selects all object in a layout, not just in a part
You can also shift-click (hold the shift key down while selecting each layout object in turn) to select a group of objects.