Carry a small dispenser-type bottle with you (the kind in the travel toiletries section at any big box store) that is less than 3 oz. or whatever the TSA deems "safe" nowadays. You can keep whatever concoction in it that works for you. I have heard of using ammonia before too, but I have sprayed a dog in the face with straight water before while on my bike and it stopped them. Sometimes stopping and yelling works too. I generally find that when I am riding, once I stop they don't care anything about me anymore. But, some dogs are just mean and want to come after you. Fortunately, I know where most of these are on my regular routes, and can either be sure and have my "Halt" ready, or have the speed necessary to blow past them. I know that this is a somewhat different scenario than jogging on a layover, but I do that too, and find that once you start to learn dog behavior in general, you have a pretty good leg up (couldn't resist) on the situation. Good luck.