I'd probably just work on my hands until I got an OK to add the legs.  Trying to do too much, too fast, too soon could prolong your recovery.  But I think you should mention to your doctor that you're a drummer and heed his/her professional advice.

I recently smashed up the tip of my left hand ring finger pretty good (bone fragments, ragged cut that could not be stitched, damaged nail).  On the doc's OK I played one gig a few days after the accident (light stuff - no head-banging), and then I was advised to stay off the hand for a few weeks.  As of now I still have a nasty nail but all else is healed up and suitable for playing.  I'm glad I got the advice early on - taking more gigs or playing too hard would have been bad in the long run.

I assume your left leg is your normal hi-hat leg?  Try going through a bass drum method book with it.

I have to agree with this completly Dave,
I had a torn medial meniscus and I told my doctor that I was a drummer before the surgery.  I put my surgery off for 4 months because I was in the works of putting my 25th High School Reunion together and I was also handling the entertainment.  Anyway, I pulled it off and
the surgery was the following Monday.  When the surgery was over I asked my doctor, how long I had to wait to play drums. He said get back into it slow and if it bothers you slow down.
You never know what your doctor will tell you? It sounds more like he wants you to rest it for another 3 weeks.   I would do what ever your doctor says.  Play with your hands.  I have really enjoyed using a practice pad here lately. Good luck with your progress.
                                           Nutty