What is the degree of the tear? Complete? Partial? Any other damage? Meniscus? MCL/LCL? I ask this because if it is just a tear to your ACL I would continue doing certain exercises, even with your injured leg. Like another poster say, bodyweight squats and lunges are good. There are some people who naturally don’t have an ACL or have a partially torn ACL and perform well in most activities.
Also, start doing quad sets where you are laying with your leg straight, contract your quad as hard as you can, and do a straight leg raise. It will all be about getting as hard of a contraction as possible. Depending on the condition of your knee, you can even do some single leg balance work in, TKEs, etc. Ask your ortho and the therapist you will work with for a copy of the rehab they are planning and start on those exercises as well.
Repeating what everybody else said, you still have 2 healthy arms and 1 healthy leg, train them hard without putting your injured knee at risk.
Best of luck with your surgery and recovery! Out of curiosity, what type of surgery are they performing? Autograft or allograft?