There will probably be two or three like this on any one visit. Have them speak calmly and in a friendly manner. Backing away or refusing to say hello are not good signs. You probably have a couple of animals in mind now. Ask the staff if they may be taken out of the cages one at a time.
Most dogs are pretty wild when they first come out of confinement.
That's to be expected and often does not reflect the dog's true nature. Once you find a dog that is friendly to the kids, not too barky, and calms down a bit when given a chance, adopt her. That way you'll be all set up when you bring her home. Don't be surprised if she's a bit depressed the first few days. No matter where you get your adult dog, a new home is a big change.