Don't fight back. I skimmed the thread and saw a couple of people giving this advice: don't do it. These people have numbers and experience on you. It would be pretty much impossible for you to win, even with weapons like pepper spray which you don't have any training with. They will beat you up before you have time to process anything since you're not used to situations like that. It takes a lot of training and getting into real fights in order to gain any sort of competence at fighting. I think your best bet is, if calling the police didn't work, move or take a different route to get to where you're trying to go.
How did this start happening?