Transportation in New Caledonia
There are 19 car rental agencies in Noumea and car rental agencies in Isle of Pines, Lifou, Ouvea, and Mare. You could rent a car for the day from most Noumea agencies (providing they have the cheap models available) for the cost of two taxi rides to the the Giante Supermarket and back.
Point Rouge (Red Dot) car rental agency is a easy 8 minute walk from Port Moselle Marina and offers the best special car rental in Noumea.
Hertz is a little further away but both will deliver a car to either Port Moselle Marina or Port Sud marina.
New Caledonia Bus Lines
The metro bus line is well developed in Noumea and you can buy tickets from automatic dispensers scattered (hidden really) around town. It is less expensive to buy the ticket from the machine than paying when you climb aboard. A one hour ticket costs 150 cfp (200cfp if you buy it on the bus). You can also buy a tourist day pass for 650 cfp. The Rocket Guide to New Caledonia has the bus routes and ticket venders overlaid on the aerial images of Noumea.
If you just need a taxi call 28 35 12 and, if needed, ask for a driver that speaks English.