I don't think this is true. I went to San Deigo a while back. I visited every possible vantage point to see the harbor, from both sides. I took the harbor tour multiple times to take pictures of the navy ships and observe their locations. I also took photos of ships leaving and entering. I took notes on Navy patrols and SEAL training missions. I drove by the Navy base mutiple times. I observed the bridge and learned about its construction. I even got a former Navy person to tell me what would happen to the harbor and the fleet if the bridge were knocked down, and where all the former admirals currently live. I also spent time looking at the North Island base using high power telescopes, observing flight patterns. I never saw an arab terrorist anywhere.
well in all honesty I think it would be relatively easy to conduct an attack similar to the attack on the USS Cole. The harbor is large, and boats roam basically freely within it. Of course the problem with going for dock boats is the casualty rate would be low, so terrorist might try to find "better" targets.
They are actually not trying to kill as many people as they can. They try to screw the US economy because they dont like the US government, democracy and the capitalism. That's why they attacked the center of capitalism (WTCs), Pentagon and possibily the white house. So in this case an attack on a place like the golden gate bridge could be on the agenda since that would hurt the counrty economically more and it doenst require as sophisticated job as we saw on sep 11th.