Are there any good exercises i can do while i'm waiting to have surgery on my acl?

Yes: You can work on upper extremity exercises and also work your unaffected lower extremity with a stationary cycle. For your affected leg, a program of hamstring strengthening will complement the goals of restoring stability to your knee since the hamstrings work synergistically with your ACL to prevent anterior instability.

Yes: The better the range of motion and strength of the leg before surgery the better you will recover. Prehab is doing therapy before the surgery. Exercising the other leg helps prevent atrophy after the surgery as well.