I never stopped lifting entirely.
On the advice of the PT, I cut out all forms of benching, flyes, dips, and overhead pressing (and any other movements that irritated the shoulder). Really the only shoulder work I was doing was the PT. I was able to continue with movements like rows, curls, some tricep exercises, and legs.
After a couple of weeks, I started doing some unilateral DB benching and overhead pressing with my right side (my left side was the bad one). I just couldn't stand the total layoff. I just made sure to keep the left arm totally immobilized during the movements.
It took about 12 weeks before I was able to get back on the bench again, for some light work. I've been back at it for about 8 weeks now. I started really light, and I'm still not close to approaching my all time best, but I hit 3X5 with 295 pounds last week with no pain. My left side still needs to gain some strength back, but it's improving. I'm no longer under the PTs care, but I continue to do the prescribed rehab exercises at least 3X a week. I've slowly added back in some of the other movements that caused pain, like flyes and dips, even some light overhead pressing (the PT basically told me that overhead pressing should be out for me, for good, but I'm not cool with that...).
My biggest advice would be not to rush it. You will know when you are ready.