Search for "LSUIPresentationMode" (you may want to use a plist editor). It will look like this if you use a regular text editor: <key>LSUIPresentationMode</key><integer>4</integer>
If the property does not exist, then you can create it - it must be inserted in the correct alphabetical order.
Change the value of the integer to 0, 1 or 2 (but NOT 3 or 4).
Along with menubar permanent display, 1 also hides the dock (until mouse is moved there) and 2 removes the dock.