You can never have too much time on the islands, a fact the many expatriates living there will cheerfully confirm. But most of us are on a tighter schedule. If you have only a few days or a week on the Bay Islands [1], you’ll probably end up choosing between the three.
Which island to visit is really a question of personal taste. All are surrounded by coral reef.
Roatán [2] is by far the most popular, with plenty of great beaches, towns, services like hotels, restaurants and dive shops, and places to explore to keep divers and nondivers alike happy for a week or more.
Utila [3] is smaller, with only one town and a couple of beaches, and is generally more popular with those focused on diving and the low-budget international traveler crowd. Nondivers will likely only want to spend a couple of days here.
Guanaja [4] is much less frequently visited than the other two, but it has equally good reef, a few hotels and dive resorts, and many deserted beaches to wander. Divers may want to stay a week, but nondivers again will likely feel content with a few days for R&R.
Those planning on doing some serious diving or taking a four-day scuba certification course will plan on five days or a week, with all the amazing diving on offer. A week or more would allow for trips out to more far-flung dive sites, which are often in the best condition. Many of the dive resorts on the islands specialize in weeklong dive, room, and meal packages, often around US$1,000–1,800 per person.
All three of the main Bay Islands [1] are serviced by air flights Monday–Saturday, and Roatán has flights on Sunday as well. Utila and Roatán also have daily ferries to and from La Ceiba [5], and ferry service from Trujillo [6] to Guanaja is available twice a week. There are a few charter air and boat services as well. Both air and ferry service can be suspended in the event of bad weather.
October and November are the rainiest months, while high season is mid-December through May (although there can still be frequent rain in December and early January). September can be a great time to visit, taking advantage of low-season rates, but typically enjoying good weather.
Links:
[1] http://www.moon.com/destinations/honduras/the-bay-islands
[2] http://www.moon.com/destinations/honduras/the-bay-islands/roatan
[3] http://www.moon.com/destinations/honduras/the-bay-islands/utila
[4] http://www.moon.com/destinations/honduras/the-bay-islands/guanaja
[5] http://www.moon.com/destinations/honduras/the-north-coast/la-ceiba
[6] http://www.moon.com/destinations/honduras/the-north-coast/trujillo