Yoron is tiny, only about 20 square kilometers, and has a population of about 6,000 people. It does not "feel" like the other Amami or Okinawan islands: it is similar to a rural village in the ocean. Chabana (茶花), located on the west side of the island near the small airport and ferry port, is the main population center of Yoron. While tourism is part of the local economy, it is geared more towards Japanese than Westerners. Hotels are not luxurious compared to those on the larger islands.
If you're looking for nightlife or a wide variety of activities, Yoron is not a good option. However, if you want a sleepy island with pristine beaches and crystalline ocean, Yoron may be a well-kept secret.
There is almost no spoken or written English. Be friendly, respectful of locals, and willing to get by without English.
Round trip ferries depart from Kagoshima City's south port daily, stopping at the Amami Islands, including Yoron, and continuing to Okinawa. These are serviced by Marix  and A-Line  Ferry companies. Fare is about 13,000円(yen) to Yoron from Kagoshima City. There may be additional ferries to other parts of Japan, such as Osaka, from time to time.
Ferry departures change from time to time, but in general resemble the following: Ferries depart Kagoshima at 18:00 and arrives at Yoron the next day by 13:40, continuing south to Okinawa at 14:00. Return ferries arrive at Yoron from Okinawa at 11:45, and depart for Kagoshima at 12:10, arriving the next day at 8:30.
The walk from the port to most accommodation is significant, but very doable and even pleasantly rural. Make arrangements if you want to skip the short walk. The taxi companies are Minami Taxi(南タクシー tel. 97-3331) or Taiyo Taxi(大洋タクシー tel. 97-2161).
You may want a rental car or scooter to travel around Yoron, as there is almost limited transportation. If you want to rent a car, you need an international driving permit - the rental agencies on Yoron are more strict than in other parts of Japan. Nankoku motors (南国モータース tel. 97-2141) Yoron Rent-a-car (ヨロンレンタカー tel. 97.3633)
However, there is a bus that tours the the tiny island several times daily, going in a circuit both north and southward. In Chabana town:
Southbound buses leave at 8:32, 11:32, 14:32, 16:02, and 18:32
Northbound buses leave at 7:32, 9:32, 10:32, 13:02, and 17:42
Additionally, though a bit inconvenient, roughing it on foot isn't impossible on an island of this size.
Besides diving or snorkeling, the main attraction of Yoron is the pristine beaches. Since Yoron is so small, the beaches are small; the biggest are a few hundred meters long, but you'll have them mostly to yourself.
There is a cultural museum and shrine on the island's hill called the Southern Cross Center(tel. 0997-97-3396). It is worth a look if you have some extra time on your hands. Entrance fee is 300円 for adults (150円 for children) and hours are 9:00-18:00.
There is also a nice little garden called the "Yunnu Rakuen" （ユンヌ楽園）, which is the island's name in it's original language followed by the japanese word for paradise. You can see traditional huts once lived in and a variety of plant life, some of it looking very exotic indeed.
Far from town is a campground near a stretch of beach from which a sandbar called Yurigahama （百合ヶ浜） can be seen rising out of the ocean when the tide is right. There are boat rides to the sandbar for about 2000円(yen), and if you are an extremely strong swimmer, you should be able to snorkel out to the sands.
There is also a small cave shrine on the island.
There is a "folk" village on the island with traditional huts.
These sights and many more are on a map available for free at the sightseeing center (tel. 0997-97-5151) near the bus stop in Chabana. You can't miss it.
Diving, glass-bottom boat rides, riding a jet ski or kayak, and wind sailing are all options. While the coral around Yoron is healthy, it tends to be rather dull colors. However, a wide variety of fish populate the waters. A single coral head may have 50 or more species of fish. Certain times of the year bring small local festivals as well.
Almost all restaurants and food stores are located in Chabana.
Wherever you go, you might like to give the Amami islands' brown sugar shochu a taste.
There is a campsite at Yurigahana beach on the east coast of the island. It costs ¥350 per tent per night, and there is also the option to rent a 'bungalow' (a one roomed mushroom shaped structure atop a pillar, in which 2 people can fit comfortably and perhaps 4 at a squeeze) for ¥610 a night.
Hotels, and traditional Japanese guesthouses are available on the island. Traditional guesthouses tend to include meals at set times, but sometimes a discounted room without meals is no problem. Most accommodation is organized either around Chabana, on the west side of the island near the ferry port and airport, or on the east side of the island (near the campground). There are about 12 places to stay on each side, mostly guesthouses with a couple hotels or resorts. The sightseeing center (tel. 0997-97-5151) can make recommendations or provide phone numbers for each place (again, English is unlikely to non-existent on Yoron).
Yoron does have a small hospital in Chabana (tel. 97-2511) and a few clinics.