@turquoise-- Have you tried forums? I think you may have better luck with those than the actual store websites, people tend to be pretty honest on forums.
You could also go to the store and ask them if you could call one of their customers. Or you could ask to stop by while a customer is getting a braid and see it for yourself. If you've had your hair braided before, it will give you an idea about how much expertise they have and if you like their work.
I don't see why a salon would refuse to let you see their work or speak to other customers if they are a good salon.