I've torn my rotator cuff 3 times. Partial, full, then partial again. No PT is a bad idea. I quite the PT the third time and it's taken me 3 years to get back to being able to use the shoulder and I don't have full range of motion.
I'd strongly suggest some PT, I also love the electrical stimulation stuff (that's not what it's called ).
But, the worst thing you could do is nothing, keep on doing what you want to do, including cycling... and don't let it stop you.
Good Luck