Open any document, this is required so that "Full Screen Mode With Menu" is available in the menu.
Start recording a new action..
From the Action Palette flyout menu select "Insert Menu Item..."
Then View - Screen Mode - Full Screen Mode With Menu
Stop the recording.
Now goto File - Scripts - Scripts Event Manager
Tick the checkbox " Enable Events to Run Scripts/Actions:"
Select "Open Document" for Photoshop Event
Select the "Action Radio Button" and select you newly created action.
Click the "Add" button then the "Done" button
Now every time you open a document it will run your action to put the screen mode to Full Screen with Menu.
Hope this helps.