It happens here ALL the time, too! My boss and I walk her dogs every day before I leave, and one day last week we had one loose dog coming at us from the front, another from the rear (separate owners, BTW). Somehow we managed to get out of it with everyone in one piece. The stupid owners of the free dogs never seem to think there's an issue.

Wish I had some advice, but all I can say is, I feel your pain!