In 2014, and early '15, I had 4 cortisone shots in the L5/S1 region due to a herniated disk that was displacing the bundle of nerves going to my left leg. All but one gave me fantastic results for 6 days (first treatment) to 2 weeks. About 3 months after the last shot, the material that had herniated from the disk finally dissipated and I have been pain free ever since.
Cortisone injections make me feel about 20 years old again, and tend to make me stay awake and want to do stuff. Last one had me up all night stripping the cabinets in the Spartan, working all of the next day, then staying out late that night with my wife, and some friends at a show in Raleigh. The procedure itself was fairly uncomfortable; a burning, almost electrical sensation from the point of injection, all the way to the ball of my left foot was intense at first, but faded to novocaine-like numbness in less than a minute. The numbness lasted about 3 hours, but did not impact my mobility at all, or cause me any distress.
I'm not sure if my experience is congruent with a lumbar facet injection procedure, but any procedure that has to do with the spine is anxiety inducing. I hope yours goes well, and bears some positive results.