I'm not convinced that anything would have achieved any particular outcome - reality just isn't easily predictable like that.
My experience tells me that you're better off:
1) Hanging up on your girlfriend
2) Calling police
3) Walking (not running) to the most public, well lit, occupied area you can find.
4) Wait for the police arriving shortly.
And what if Zimmerman was simply out to shoot someone?
Your methodology seems to say "take your chances - give the benefit of doubt to this stranger who is clearly after you and who you have no reason to believe is NOT dangerous"
Really? Slow down, become a more accessible target, make yourself more vulnerable to immediate harm or abduction?
That just sounds like a predator's dream come true.
IF (and I am not saying this is the case) but IF Zimmerman were actually a predator hunting for a victim using the guise of being a neighborhood watch captain in a gated community - and had Treyvon done as you suggested and NOT run (there's no guarantee that he could have gotten 911 on the line before a bullet prevented him from continuing to live) - then Z could have simply popped him and rolled on. There wouldn't be all the other 911 calls that heard (what I would tell my kids to do) someone running for their life screaming "help!!" There would have been even less evidence of anything because in that story, Zimmerman wouldn't have even had to leave his car and could have easily claimed "car-jacking gone wrong" - "protecting my rolling castle" - "I was just going to say 'hi' and he went crazy so I had to shoot him"...
At least by running, Treyvon aroused a lot of attention, got a lot of people to call 911 and there is now, in light of the fact that you clearly couldn't rely on the police to do their job properly, at least some evidence of what happened.
Had Treyvon taken his chances, as you suggest, this could have all been a non-event (I doubt it) - or worse, it could have been a "good shooting" because of all the additional stuff Zimmerman could have claimed by staying in his car.