How much can you handle? How competitive are you as an applicant? Where do you want to go relative to where you are? It comes down to these questions.
If you are competitive (excellent board scores, multiple honors, excellent letters), you may not need 3 aways. However, ortho is competitive no matter what people tell you, so I personally would do at least 2.
How much can you/do you want to handle? 2 aways plus your home institution is already 3 months of one subject, and for me it was all back to back-"no sir although I'm post call I'm fine"-"no I'm not hungry, can I stay for another case" work my butt off rotations. As much as I love ortho, after 3 months, I couldn't stand any more anatomy (however, I knew my shiznit by the 3rd month, so I looked pretty smart, at least I think). I have a friend who is trying to go to Cali from the midwest, so he did 3 aways in Cali plus our home institution. He was dead furkin tired by the 3rd one, but he also said he thinks it was worth it. I don't think I could have stomached the 4th month.
I personally am going to the East coast hopefully from the midwest. I rotated at 2 places in Philly, which has 5 programs. The other programs at which I interviewed in Philly didn't look down on the fact that I didn't rotate at their program, rather they took it as a positive thing that I was committed to going to Philly. It was awkward however when I told places in NY that I rotated at 2 places in Philly, but that's off the topic of how many rotations should you do.
Try answering these 3 questions first, and hopefully it will give you a better idea of how many aways YOU need to do.
