Small does not necessarily mean they need less walks. I have a 25-pound Schnoodle (Schnauzer/Poodle mix) and he was extremely high energy, requiring several walks and a daily trip to the dog run to let off steam until he was about 11 years old. Once he turned 12 he mellowed out but he is 14 now and still has the energy level of a 6 year old!
I would steer clear of the Terrier group actually. Someone mentioned Shi Tzu, which is a good idea. Also, although you can generally predict a dog's behavior by their breed, every dog is different. Like people, dogs have their own personalities and I'm sure when you meet the right dog you'll know.
Jacqueline, I think it is just wonderful that you are going to get an older dog! Everyone wants puppies but older dogs are so much less hassle and getting one through Petfinder is such a good way to go. I know several people who have gotten their dogs on Petfinder and they are fantastic companions!
Keep us posted when you decide the time is right... and I'll want to see pictures.