I'm sharing this article because the stray this family rescued reminds me so much of Blizzard (she was also a stray), whom I found at the local SPCA several weeks ago. You do have to be patient with them. Link: Voice lessons: An adopted stray rediscovers her bark - CSMonitor.com
Blizzard was also quiet for a long time after we brought her home (we did see and hear her bark once in her pen at the SPCA); and her coat was so thin I worried about it, but it's much thicker now, and she's more confident, though I have to coax her into the car, which is easier than picking her up which I had to do for a long time. One thing about an older puppy, I did not have a hard time house training her. As a matter of fact, she required no house training at all! (She puddled on a rug once. You do have to be alert.) I remember one puppy some years ago who shredded her papers (on the bedrom floor) into confetti constantly. There is a wonderful selection of loving dogs--and cats--at your local shelter. Find out for yourself.