So, newbie here, is it possible for me to clear a town?
By default, yes. The zombies you see in town at the start at the only zombies in said town. No more will be made.
That is, unless you go into the options and turn off Static Spawn. If you do that, they’ll keep spawning. But, by default you can clear a town.
So what should I use to attract them to me?
If you want zombies to attract as many zombies as possible, then the best way is to set fire to a building or fire a gun. The bigger the gun (or building) the louder it is. Though, it’s usually pretty easy to attract a horde of zombies just by entering the city. I have a hard time trying to keep the hordes OFF of me. 
Sweet, I’ve got a plan to clear out a city and then build palisades around a house or something, burning a house down would give me lots of material too. I wish you could build those heavy garage doors on a house.
You can create a palisade gate, which is activated with a pulley system (similar to those barns in farms). Not sure if it’s already implemented in 0.3, though.