I have a Pearl Harbor question, too!

I believe that the U.S. had information (through breaking the Japanese
"Purple"* code!), that an attack was going to be made on one of several Allied
targets;(including Pearl Harbor!), at the time of the attack. Given that, (IF
it is true!): WHY did the U.S. Navy NOT move the Pacific fleet to a place of
safety; (like, say, the West Coast)? No good ports; (given the existance of the
ports of Los Angeles, San Fransisco, Portland Oregon, Seattle, ect; I DON'T
THINK SO!)?

Even IF the Japanese had a plan to "Pearl Harbor" a West Coast port; I would
think that the U.S., Royal Canadian, and/or Mexican Navies would realize
something was up in time to give SOME warning! (Just from NORMAL military,
fisheries protection, or "Coast Guard"-type activity!)