The Auckland Allies series takes place in Auckland, New Zealand, beginning circa 2015. Most of the public places mentioned really exist, and you can see them on these specially-prepared maps. Click the pins for labels.
This is the map Sparx prepares in the first book (Auckland Allies), showing the dastardly plan of the Blokes in Black:
This map shows the journeys around the downtown area that Sally takes (one of them with Sparx), pursued by the Blokes in Black. There's a video showing the Sally/Sparx journey on the Background Information page.
This map shows the area around Grafton Bridge where most of the action takes place in Auckland Allies 2: Ghost Bridge: