Firstly, it's great to see you're dealing with this in a fairly calm manner.
The dogs shouldn't be getting out in the first place; you could consider calling the local authority dog warden about this. The most likely outcome is that they will get the owners to improve their fences.
Running is the worst thing you can do. With your dodgy joints, there's no chance you'll outrun them, and the "thrill of the chase" is a very real thing (see also: my dog who always chases squirrels and cats but slows down if he gets a bit too close because he doesn't know what to do next....).
Chances are they're running up to you because they're bored, and you're the most exciting thing in the vicinity. The best thing you can do is to be very, very boring. What do I mean by that? Stand still, turn your back on them (repeatedly if needs be), fold your arms and don't scream or shout. Basically, do your best impression of a tree. I've used this on everything from overfriendly dogs that jump up to barking ones which are less than friendly, and it's very effective. It's also very non confrontational so if the dog is unfriendly you will deescalate matters.
I know you're nervous about dog bites. I'm going to give you a bit of info so that if you ever did feel teeth, you're less likely to panic and make things worse. Firstly, all dogs when young will chew as part of a developmental stage; it's known as puppy biting and it's just like when toddlers go through a stage of sticking everything in their mouths. Most dogs stop doing this as adults, through a combination of growing up and training. Some continue a bit longer than they should; I used to have a neighbour with a free range dog who periodically gave my arm a gentle chew but meant nothing nasty by it. Secondly, the good news is that dogs naturally have what's known as bite inhibition; they'll chew a bit as part of play but not as hard as they can because they don't want to cause damage.
From your description, it sounds like the chances of them running up to you, jumping up to say hello and even getting your trousers dirty is relatively high (and it's unacceptable, but not the end of the world), but the chances of them doing you an actual injury by biting are very very low.
The product @ToBeOrNotToBee linked to is very vague on the composition of what's in the spray, but it's a bad idea as
A) a dog which is disoriented as the marketing blurb suggests may bite when it otherwise wouldn't
B) if it's pepper spray, CS gas or similar you're committing a criminal offence by having it.
C) it's almost certain to make relationships with your neighbour go south and quickly