I've had bad experiences with dogs off leashes too. The only time we ever got attacked was as I walked my two on leashes as usual and a huge golden retriever charged out of his yard -- by this time we were half way across the road- and started fighting with Star. She ended up with puncture wounds under her jaw. I called the animal warden. He said the retriever would have to be kept tied up, which the owner objected to because she had "invisible" fencing. Obviously it was very invisible, her dog couldn't tell where it was.
On another walk a small dog came running across the road (a fairly wide street) yapping right in Star & Rosie's faces from it's porch WHILE THE OWNER STOOD THERE WATCHING I was really worried they would grab that little mut and injure it - they don't like being barked at. It took all my strength to hold them back while the owner STILL stood on his porch doing nothing. I slipped and got dragged across a tree lawn screaming when this a*#@!! finally decided to come grab his pint-sized terror. The jerk never asked me if I was ok, or helped me up or anything. I was furious. I have to say I like taking my dogs to a dogpark a whole lot better. Much less dangerous.