One of the best ways to get from Coronado to Downtown San Diego is to take the Coronado Ferry. You can buy tickets from an automated machine on the Ferry Landing pier.
As of January 3, 2011, adult tickets are $4.25 each way and children under 3 are free. Bikes are allowed at no extra cost.
See the Coronado Ferry schedule and get ticket prices here.
Commuter Ferry service is a Fare Free service provided by the City of Coronado for residents and Military of San Diego and Coronado. Please note the times the Coronado Ferry runs. More details here.