The default place is the DAE>Plugin Settings folder, then look for "Eleven Rig"
Have you saved any rigs to the computer yet?
Also you do not have to save to the default place which is the OS hard drive, I always save to an external myself.
If you can't find where you last saved your Rigs, go into PT open up the Eleven Rack on-screen Editor and save a rig or all rigs to computer, that should bring up the location where rigs were saved to last, then just look at the branch and go to it.
I talk a bit about saving rigs in the following video:
http://www.youtube.com/watch?v=t3ClWRi2Fzo