Hmm.... both have tactical advantages that are also disadvantages. If you still have your pipe with you, then I'd definitely recommend the streets, though, just because, as TSO said: easier to break lose in case a horde approaches. Plus, it'd allow you to actually see the zombies coming. Generally. So, I'll say B.
(Just a quick question, but these are REAL zombies, right? Like, reanimated, rotting corpses that will consume you and turn your remains into one of their own, assuming you can't outrun their slow movements due to their loss of motor function? Not the mutant zombies of, say, Resident Evil or L4D? Just curious to know what kinda zombies you're talking about here. =3)