I would say that a majority of programs grant rotators an interviewer unless you just completely mess up in which case you don't deserve one. Those programs that don't invite rotators are probably the ones that you don't want to go to in my opinion. Some programs actually will interview you while you're doing your rotation so you don't have to come back during the hectic interview season. Some programs give info on their website. You could always email or call them, but that might be inappropriate?
As far as number of interviews, I would say that if you do 10-12 interviews, then you're sitting pretty. There's only so many number of interviews you can go to as many overlap on the same day. It maybe that you get 20 invites, but can't realistically make it to everyone. Just be sure that you don't overshoot by going on a big name that everyone wants and ignore some of the smaller programs. No matter the program, you still become an Orthopod.