From: Northwestern Georgia, USA
I would also be leery about Suva, for the same reasons as Noumea: forward base, exposed to enemy envelopment, and the enemy has more than one base to land at, making use of CD guns problematic.
I defended Fiji in my games against Q-Ball and Miller, because circumstances permitted me to do so (mainly, my opponents were occupied elsewhere, which bought me the needed time to really make defense possible and worthwile). I did not defend Fiji in my game with Chez Da Jez, because he moved quickly into SoPac, taking it before I could organize a defense that made sense.
Through mid 1942, Japan can choose where it wants to go and the Allies have little chance of stopping them (except at the major bastions, of course, includng Pearl, West Coast, Oz, and India). However, the Japanese can't go everywhere. Thus, for the Allies, it is a bit of a dance - identifying where Japan is going, slowing Japan down when possible, and taking advantage of places where Japan isn't to build some good bases.
In most games, I would identify key forward bases that I will try to garrison at the outset - in most games I'm going to immediately focus on some of the Aluetians, Pearl Harbor, Christmas Island, Tahiti and probobly Pago Pago. Decisions about other important Pacific bases including Fiji, New Caledonia, and even New Zealand, are postponed a bit until the situation develops enough to permit analysis and good decision making.
As for Lunga, Port Moresby, and Luganville? Forget them, unless I'm facing a newcomer or I'm feeling particulary robust, feisty, and "devil-may-care".