MN Bianchi
My last knee surgery was in 2002 so my situation is a bit dated.
I too had a torn medial meniscus repaired on a Tuesday morning and the PT had me doing squats on Thursday. The PT also had me doing some spinning at the same time. I was told to take things easy but to let my body be my guide. My PT later went to the Olympics as one of their therapists so I feel like I had the services of a good therapist.
Personally I wouldn't rush things and I would also ask the doctor.....not the PT...about any serious riding. As good as a PT may be, the doctor is the one who saw inside your knee.
This is in sharp contrast to twenty years ago when I was off two weeks and told to use crutches for the same amount of time.