GNOME's StickyNotes applet does not provide a keyboard shortcut to open all notes on the desktop. The following command can be associated with a keyboard shortcut, whether in Metacity or Compiz, to perform this task, once the wmctrl package has been installed:

for item in `wmctrl -xl | grep "Stickynotes_applet" | awk '/0x.*/ {print $1}'`; do wmctrl -i -a $item$; done