Seriously though, if this does happen, run. Move quickly. Disregarding the fast zombies, anyone in adequate shape can outrun them. If you stay and fight, yeah you'll be able to take down several of them, but you'll get overwhelmed eventually, regardless of your weapon, be it a Mossberg or a crowbar.
I think this is the one situation where "stay and fight" gives you less chances for survival.
Come to think of it I think your county jail would be the safest place when such an event happens.
Allow us to analyze the most prominent zombie-featured game series (since there is no zombie-prominent movie series): Biohazard. For one, Pfizer is not there yet. For two, either the RPD has no training (expect for, well, Leon) or they just don't know when to retreat upstairs, which loops back to the "lack of training" part. For three, again with the fast zombies! Unless it's a mutant uprising, putrid tissue cannot jump over fences! For four, nuking the city and tell America "it's a reactor meltdown"? Americans aren't sheeple! So Umbrella somehow controls the actual U.S. Army, but this just loops back to the whole "Pfizer is not there yet" issue.
That said, a mutant or robot uprising is a whole other issue. If this was to happen then our opponents will have all kinds of superiority over us. The CDC can most probably contain the former and the latter, well, I'm sure that GLaDOS can stop it. That is if it isn't GLaDOS herself who started it...