Hi Rob,
If your on the main island then I have fished on the Coral Coast (halfway between Nadi and Suva) at a place called Mango Bay Resort.
The owners are a American guy, Bret and an Aussie guy, Danny. Bret has a serious fishing charter set up, and is ever enthusiastic to get amongst GT's, reefies, pelagics and game fish. He has 2 boats and his crew/deckies really know there stuff.. I would definitely look him up if I were going over there (which I am
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Google mangobayresort or sportfishingfiji and I think you will find them. Had a few magazine articles praising them seen over here also.
Alternatively if you want to go remote, then look at the outer areas, but that takes a bit more time and research to find a good set up.
I made it over to Kadavu last october and Fiji was experiencing an awful month of weather and pumistone choking the waterways. Fishing was not good by there standards. Hopefully this summer will be great.
cheers Dave