Probably not for free. Stern's show is available on XM Premier (formerly known as the Best of Sirius add on) package from XM. XM Premier costs $4 more per month than XM Select. You should call XM and ask if you can pay for the difference between Select & Premier if that's what you want. On top of the Standard XM channels, XM Premier includes Stern, Martha Stewart, Playboy, NFL and NASCAR.
I know that add-on's are available with the free subscription, as I am still getting the Online package for only $2.99 per month as an add-on to my free subscription. Since dropping the "Best Of Sirius" add-on for the XM Premier package, I don't know if there's still a way to bump your subscription up or not.