Ubuntu has a built-in utility for assigning shortcut keys. Go to System \ Preferences \ Keyboard Shortcuts:
Scroll down to where it says “Run a terminal”, and click in the Shortcut column. When you see “New accelerator…”, the next keystroke that you use will set the keyboard shortcut.
I assigned Ctrl+Alt+X as mine…. one press of the key combination and up pops a terminal. What a time saver!