Just check on your district and state laws if you carry spray. Your laws tend to be more liberal than ours but here it's actually illegal for someone who is not a police officer or similar to carry and use sprays. I agree a horn sound is excellent. You could look at a taser also and consider the legalities of that too. Your local police station should be able to offer good advice.
I was mauled by a dog as a child. Not fun. I love dogs but once or twice in my life I've been confronted by a dog who I knew was poised to attack. I slowly walked backwards with eyes lowered because meeting the eyes can be taken as a challenge (like in dog packs).
I believe bad dog owners are becoming a major menace in our society. No-one should be scared to walk down their street. In my current area there are a number of heroin users and for some reason most have dogs. They wander with owners with no leash, most are ill fed and a few have had way too many litters for their own good. I've got back into my car on one occasion rather than risking walking past a pit bull walking up the sidewalk.