As others have stated here, there is no need to engage the owners verbally when you are the one who is engaged in a legal activity.
Do not get mace, get pepper spray. You can buy the stuff used outdoors at a Bass Pro Shop or Cabelas. Works on bears, which are very similar in physiology to dogs as far as how they react to pepper spray.
If you know dogs are in the area, then slow down. If you peddle by them at a slower pace, the dogs tend to ignore you.
I was just on my 17.5 mile ride out in the country yesterday and a mile away from home, when I looked ahead and saw a pitbull ahead of me in the road...I applied the brakes and shifted up into a higher a gear, and peddled by at a snails' pace...never heard a peep from the dog and never looked directly at the dog either...