pet dogs turn into wild dogs.

[Devonian]

Having done a quick bit of research on this I think MaryN's response is probably closest to what is most likely to happen based on existing evidence of feral dogs that are roaming around cities like Moscow, Serbia, Romania and many of the major third world countries cities.

http://en.wikipedia.org/wiki/Stray_dogs_in_Moscow

http://en.wikipedia.org/wiki/Street_dog

Generally stray/feral dogs will see humans as the greater threat to themselves and will therefore avoid contact in times of hardship and if we use consider CH's post, we can see why

There will always be exceptions, but generally as long as you don't corner a dog or threaten them, they will normally leave you alone and instead look towards the rubbish and waste to find a meal.

They are also more likely to turn upon the weakest members of their own packs, though you wouldn't want to be cornered or encounter a pack of feral dogs down a dark alley, especially if you are injured!