That's probably a good bet. Pediatric ortho is not the most popular field within orthopaedics, and I have not seen many programs emphasize that particular field during my interview trail. Having a well known, prestigious, busy children hospital, you'll most likely to have many peds attendings and dedicated teaching. Obviously, there are other factors that play into it, and these do not guarantee anything. Many residency training programs will not focus on their pediatric hospital (particularly if they don't have one), but since most applicants don't have much interest, not many people care.
CHOP, UPenn: UPenn has a great relationship among residents and attendings and with CHOP right next door, it's probably one of their biggest strength. All the students who rotate through CHOP simply raves about it.
Harvard, Children Hospital of Boston: Obviously an awesome program. Other residents from nearby programs rotate through this hospital as well to make your call schedule easier. Training is worldclass, with worldwide referral.
Case Western: one of the best teaching overall in terms of residency training, and has a children hospital ranked very high and also prestigious. I don't know too much about it... but I'm sure their great training atmosphere spills over to their children hospital as well.
Columbia: the only major children hospital in NYC, and probably the strongest in the city. And, it's columbia... love the program!
Brown: everybody talks about their awesome trauma, and great operative experience, but realize that the chairman of Brown (Dr. Erlich) is a peds ortho guy. I'm sure they kick some butt too in their peds training.
Others to look at: UCLA, Wash U, Johns hopkins, U of Wash.
I'm sure other programs without children hospital can provide more than adequate training, but having a dedicated full hospital to pediatric conditions might be a huge plus.