Fiji is one of those places that sounds like a fantasy until you actually price it out. The good news: May through October is the dry season, which means less rain, calmer water, and the kind of turquoise you came for. The trade-off is shoulder-season pricing, where flights and stays dip compared to the December peak. Stick to the main island of Viti Levu at first, take the ferry or a short hopper to the Mamanucas, and you can keep the whole trip — flights, a mid-range stay, food, island-hopping — in the neighborhood of $1,100 a person.
Most people do not have $1,100 sitting around for one trip, which is where timing the payment matters. Splitting that total across a few months instead of one swipe is the difference between a vacation that you actually take and one you keep pushing back.
The 0% window is a deadline, not a discount. If you still owe on the balance after 18 months, the card's regular APR kicks in on whatever is left, and that number is usually high. Treat the 18 months as a hard finish line and pay the full $1,100 before it hits — that is how this strategy actually saves you money.