I had a complete tear of the ACL less than a year ago - (from playing basketball.)
I spent as much time on the bike as I could both before and after my ACL reconstruction. I was doing wave-sailing (no jumps and taking it pretty easy on the wave face) three months after my surgery. 8 months later, I am playing basketball, doing whatever I want windsurfing, and training for a marathon. No problems.
Train for your surgery by putting time in on the bike beforehand. It is also the most important part of your therapy. I have had a great recovery that by no means should be considered standard - but I worked my @$$ off for it.