The first rule of survival is not to get into the situation in the first place through planning and common sense. I agree that the park with the crime should be avoided. Walk in pairs if you must. Fighting is a last resort as the outcome is usually not good.
That being said all possibilities should be accounted for and some simple weapons like some pepper spray and a good knife along with training will go along way in both deterring and helping you survive such an altercation. I personally carry a blade and a large can of bear spray as its stronger and shoots further for a longer period.
I am not built for speed either but am strong and can handle myself.
There is no guarantee.
Flip