I would definately leave from San Francisco. I did Mercury 10 Day Mex Riviera from San Diego last year and Port of San Diego was a mad house. Embarkation went smoothly but the return was crazy. Too much traffic and took forever to get my baggage......Its not a good way to end a vacation. Just think how nice it would be if you were home when that ship pulls in. Either way you will have a wonderful time. The Mercury is absolutely beautiful with an incredible staff. Have a great trip!