just keep clear..
i don't know what the rules are about approaching the cruise ships while they are at the terminal. i could see how the athorities would get anxious if you are loitering there given all the effort they are putting into anti-terrorist measures in the harbor.
i do know by personal experience that if you are near the path of a cruise ship when they are under way inside the breakwater you will get lots of attention real fast. i have seen them with an armed escort (coast guard RIB with a machine gun on the bow) leaving the harbor on multiple occasions and one time I was approached by those guys, and one of the men was at the bow with his hands on the machine gun. i was clear of the oncomming ship on a heading about 45deg away from its course and what i thought to be at least 100 yards from its path but they wanted me to be farther away.
speaking of cruise ships at that terminal, the queen mary 2 will be in san pedro this week. the shoreline marina newsletter invited everyone to be a part of the armada of small vessels that will greet the QM2 in long beach when it gets near the queen mary and they exchange horn signals.