My situation is a bit bifferent as my dog is much larger, 150+lbs, but he has his knees done about a month apart from each other. He had a totally different surgery, TPLO, not usually (or ever perhaps) done on small dogs, but he was up and able to bear weight the next day really. You can get dog slings that will help hold up their end while they walk around, allowing them to bear the weight of their front, while you support their back end, I used a towel for my big guy. But really I was surprised at just how fast he did recover, honestly.
If you dog is under 30 pounds and has a torn ACL and you opt to not do the surgery, you will need to get a dog cage/carrier and use it. Keep your dog confined when you are not able to closely supervise and on restricted activity (no jumping, running, going across slick floors he can slip on), leash walk only. http://mixle.com/bia-slim-review.html