you can access the menubar from keyboard by pressing CTRL + F2.via a comment on
Make sure full-keyboard access is turned on in order for this to work. From another comment on the same post:
the 'Full Keyboard Access' option in the System Preferences > Keyboard & Mouse screen. If you open up your prefs and go to the Keyboard & Mouse Prefs, then click “Keyboard” tab. Than set the full keyboard access to “All Controls” This gives you tab control in dialogs.