<alt><ctrl>F2 (or F3/4/5 etc) will open up a console terminal, one of those will be the X display on mine it's F1, sometimes it can be F10. Basically hit them in sequence until you get the login prompt and you can log into one of the tty consoles.
Edit: to be clear, this doesn't alter the run level, but it brings up a character console which looks like run level 3, which is what I thought you were looking for.
Last edited by MartyBartfast
on Fri Feb 24, 2012 8:50 pm, edited 1 time in total.
I have been touched by his noodly appendage.