I know of one student who matched at Cleavland who I think had ~avg step I score, and another student who interviewed at both schools with a below the avg step I score and avg clinical grades but who came from a top 5 med school. I think that if you aim for above avg (216+), you should be fine step I-wise.
I hesitate to use "below average" with people I know, but I know 2 students that matched at the Clinic with lesser numbers. Case is a tougher match, from what I've heard. I ended up skipping both places, but I concur with kalel -- anything average or better should get you in as long as the rest of your ducks are in a row.