No ortho/rads program I've heard of has ever required anyone to pass the boards prior to turning in their rank list. I don't know if anyone is an FMG on this post, but if so, then I might seriously think of a back up plan as well. Not to say that FMG's can't match into one of those specialties, it's just a very rare cirumstance. The question I would have for you is why ortho/rads, etc? They seem at rather opposite ends of the spectrum.
My advice is that if you're happy with Step I and that's all that you want a program to see, then wait to take Step II till after interviews. If I were to guestimate, only about 5% of people I've ever talked to have been questioned about Step II in an interview.
If you were less than satisfied with Step I, then take Step II sometime before the middle of August. It takes about 4 weeks to get your scores back and then you can decide if you want to include them on your ERAS application.