Fiji is not known as a golfing destination. To be honest, Hawaii would be your Pacific Island of choice if golfing was your primary reason for a tropical vacation. However, there are a handful of courses on the main island of Viti Levu, ranging from municipal (Fiji golf club, Suva), to resort (Denarau Island) and championship (Natadola Beach).
The three top courses are Denarau (managed by Sheraton), Natadola Beach (next to Intercontinental resort, a forty minute drive for Nadi) and the Pearl (managed by Pearl resort, Pacific Harbour) A two hour drive from Nadi. As you would expect, resort guests get discounted green fee rates, so you may want to consider that when booking your accommodation. However, they are all open to the general public so if you only want to have one or two rounds during your stay, it might be cheaper to stay elsewhere and pay the full green fees. If you're looking for cheap cheap, you will not beat the Nadi Airport Golf Club. Green Fees $30 for 19 Holes!
A 15 minute drive from either central Nadi or the airport, is Denarau Island Golf Course. A 18 hole resort style course, this caters to those that want a great round on a manicured course, but don't want to spend all day hacking out of knee high rough. Top class facilities, with pro shop, driving range, cart and club hire, and bar/restaurant.
Championship style course, located at Pacific Harbour. Lovely club house, this is a long and very challenging course. Full length par 72.