As I understand it, French is the main common language in New Caledonia, spoken by almost everyone there, but often as a second language.
The wikipedia article doesn't seem to mention much about English though. Assuming you largely stick to the more touristy areas (eg the beaches around Nouméa), can you get by with just English? Or is a reasonable level of French needed? (Or I guess one of the Kanak languages!)
There's a more in-depth article on Wikipedia — the Languages of New Caledonia.
However, the downside for you here is that while English was one of the three main languages until 1853, there was then a concerted effort afterwards to wipe it out.
The closest lexically was Bislama, although the words were different, so that might be an 'easier' one to learn if you wanted to learn some phrases in a non-European language, however, realistically, French is going to be your best bet here, it would appear.
However as you've no doubt noticed in your travels, even in places where you wouldn't expect it, people quite often know some English 'unofficially', and you may be surprised. It's also surprisingly easy and fun sometimes to communicate without words ;)
Indeed, according to Wikitravel's article on the area, if you're in Noumea, you may in fact be ok:
The official language is French, and it is difficult to find English speakers outside of Noumea. In Noumea, French, English, and Japanese are widely spoken at hotels, restaurants, and shops. To enjoy a place like this, you should really endeavor to learn some French.
I found more English in New Caledonia (Noumea, and a nearby island resort) than I did in France. Hotel staff, people selling postcards and cold drinks in the tourist areas, and airport people all had enough English for our transactions. Shuttle and taxi drivers (including boat shuttles), people who carry luggage, and people walking past on the street generally did not.
I have Canadian high-school French. This is "please", "thankyou", plus enough to generally shop, chitchat with shuttle drivers, and say "we are not ready yet". As a result I didn't notice a language problem at all in Noumea. Anyone with whom I needed to have a more nuanced conversation than my French could handle could speak English. That is in contrast to Tahiti and the Marquesas, where not having French would have been far more of an issue, even in the airport. However if you showed up with absolutely no French at all, even in Noumea, I think you would feel lost a lot of the time.
