I had good fortune/ bad fortune when it came to cycling PT. As background, when diagnosed with arthritis, I had recurring cycling problems with isochial tuberosity (sp?) muscle pulls - probably from rom limitations to step over the pedal stroke. Eventually I had to stop riding, but a friend who is a way more serious cyclist, suggested that I see his coach. His wife is an MD in PT and that year had a US national championship (on tandem)! They were able to get me re-fitted on bike to ride a year or so longer on with arthritic hips.
So I saw her again after surgery, and as somebody who really knows cycling, it was good that she had all kinds of good PT exercises. But she was extra cautious, and she didn't want me going on the road until she was satisfied that balance and strength were sufficient. She would have liked to have me riding no handed on rollers while getting knocked with a pool noodle :-) before going back on the road. I don't recall if it was 9 weeks or 12 weeks or whatever when I took my bike off the training stand and went out into the real world, but I kind of split the difference when it came to getting back on the road. The advice sounds trite, but listen to your body.
Sometime during the first couple months, while riding on the training stand, I recall trying to get out of saddle, and the muscles just were not willing. I'm not sure if I would have fallen had I not been attached to the stand, but it certainly would have required a catch of balance.
Even after 1 yr, I was still feeling some effects from the surgeries. I could slog up a long climb with no problems, but a couple times, I got some significant soft tissue pain from all-out sprints. So I laid out of the group-ride sprints for a few months, and gradually worked up intensity of output, and sometime during that 2nd year, the problem went away. Oh, another thing from the first year, that you may or may not find, I'd get a clue from my back when I had worked too hard. The good news is that all those symptoms went away.
Good luck,
-Dirk