Question: Is there any bus transportation between Varadero and Cayo Coco? Schedules and Cost?
Answer: There are no buses from Varadero to Cayo Coco. There is a tourist-quality Viazul bus that leaves Varadero daily for Santiago de Cuba, and which stops in the city of Ciego de Ávila, the capital of the province by the same name in which the island of Cayo Coco is located off the northern coast.
If you were to take Viazul to Ciego de Ávila, you could then explore local bus schedules. A taxi would be very expensive from the city to Cayo Coco. And a taxi from Varadero to Cayo Coco would be even more expensive. From Havana to Cayo Coco, for instance, the one-way charge with Cubataxi (telephone  955-5555 in Havana) is CUC 267, which is the ballpark figure for a taxi from Varadero to Cayo Coco.
If you want to explore Viazul, check out their website listed below.
Viazul, Avenida 26 y Zoológico, Nuevo Vedado, Ciudad de La Habana, Telephone (537) 881-1413 or (537) 881-5657 ext 101 / 113 (information & reservations), Fax (537) 883-6092
According to the Viazul website, which appears to exist only in Spanish, reservations can be made and paid for online by credit card. (Note: credit cards payable against US banks are not accepted in Cuba.) The website provides details about online payment.
The most economical way to travel to Cayo Coco might be by plane, specifically with Solways Cuba. In a May 2011 phone consultation, Solways Cuba said that from Varadero, the only cayo to which they provide flights is Cayo Largo (off the southern coast near Isla de la Juventud).
However, Solways Cuba has a daily flight from Havana to Cayo Coco. This flight leaves Havana at 12 noon and costs Euros 158 for a round trip ticket, which includes transfers in Havana and Cayo Coco. If you are not staying in a hotel in Havana, you would have to go to the nearest hotel where Solways provides transfers to the airport. Reservations can be made on internet at www.solwayscuba.com and payment can be made by credit card as long as it is NOT American Express.
The Solways home website is www.solways.com and the website for Solways Cuba is www.solwayscuba.com , both in English. Their page includes departure and arrival times, from which airport you depart and to which you arrive, frequency of flights (days of the week) and per person cost of a one-way flight, usually including transfers to and from the airport.
You can either book your flight online or contact the Solways travel expert in Havana (address and telephone below) or email them at [email protected]
Solways Cuba, Edificio Santa Clara, 4th floor (for reservations), Miramar Business Center, Playa Municipality. Havana, Cuba. Telephone (537) 204-5577, extension 1441 (for questions) or (537) 204-5940
NOTE: as a reference point, Solways is located next door to Cubacel, and Edificio Santa Clara is across the street from Hotel Meliá Habana.