Sorry to hear about your knee!
I did the intro ride on Saturday and really enjoyed it. Would you please pass on my Thanks to Steve for leading it out. I think I might have annoyed everyone else a bit though getting over the novelty of my new bike and the ease of limbing up the hills and setting off.
I think if I do an intro ride again, I'd take one of the fixed gears but I might have to try and gear up a bit more sensibly as 63" will be too low and 89" will be too high.