Normally the shortcut Command + F2 (Mac) | Control + F2 (Win) moves the focus to the menu bar. However, in Photoshop CS6 this keyboard shortcut is not editable since it is hard coded into Photoshop to lighten the interface. Thanks to Pete Green, here is a workaround for accessing the menu bar (Application Menus) using a different keyboard shortcut.
By default, Command + Shift + / (Mac) | Control + Shift + / is assigned to display the Photoshop Online Help. We will release this default shortcut using the keyboard shortcut editor. Once released Command + Shift + / (Mac) | Control + Shift + / will display the Search option in the menu bar. From there, you can either begin to type/search the menu item you’re looking to use, or you can just use the arrow keys from there to navigate the menus.
To clear the default Command + Shift + / (Mac) | Control + Shift + / shortcut, choose Edit > Keyboard Shortcuts > Help. Under “Photoshop Online Help”, clear out the entry for Command + Shift + / (Mac) | Control + Shift + / (you can leave the CMD+/ shortcut there) and click OK.