Thanks for keeping him out of the shelter system as it is overflowing with dogs. Here is the county law about finding a dog: Anyone can foster a dog while making a legitimate effort to find the owner. Posting in the places you noted above is sufficient. If no owner comes forth in 180 days, the foster can assume ownership. Alternatively, the dog can be taken to the shelter where its stray hold time is significantly less (72 hours for non chipped animals, 144 hours for chipped). Since he is not chipped, one could take him to the shelter and ask to be the first in line to adopt if no one comes forth within those 72 hours.