If you walk your dogs and don't carry pepper spray then I'd question your IQ.
I've sprayed a dog or two but I've also found that just spraying the ground in front of the attacking dog usually makes them stop and then retreat. Another tactic I use is "command voice", make the dog know YOU are the boss in that situation and they'll usually back off. Now, I'm not some naive fool, I know there are dogs out there that'll attack just the same but a face full of pepper spray WILL stop an attacking dog and save you a major hassel with an LEO or a civil suit. Of course, the dog owner is going to be really pissed about his dog getting sprayed, just keep that can of spray in plain sight!