Once you arrive in San Juan, you can either fly or take a ferry boat to Vieques.
Ferry
It takes about an hour and a quarter to drive to Ceiba Terminal where you get the ferry boat. In October, 2018, the terminal in Fajardo was closed. The ferry takes between 35 minutes and 1.25 hours to arrive in Vieques from Ceiba, depending on which type of ferry you take.
Flights
The flight from San Juan International or the San Juan city airport takes about 25 minutes to arrive in Vieques. The flight from Ceiba airport takes about 7 minutes.
Car Rental in San Juan
If also can rent a car in San Juan and drive to Fajardo or Ceiba. Car rental companies do not allow the rental car to be taken on the ferry and reservations are difficult to obtain.
Car Rental in Vieques
There are many rental companies in Vieques that will rent a car, jeep or SUV. See this directory: https://viequesinsider.com/vieques-vacation-planner//#getting-around. Sometimes you can get one at the last minute, other times you must reserve the car weeks in advance. You do not need a “Jeep”: any SUV will suffice to travel to the popular beaches. The average price is $85-100 per day.
Bikes
Biking is a good “green” alternative to renting a car. Link to Bike Rental information.