L.A. IS a high profile target. The actual target building is not terribly important in this case, so long as it kills a lot of people. Los Angeles is on the West Coast, a liberal area so far free of any major terrorist activity. It is also a very well known city, like New York, that everyone in the world will have heard of. The PR value would be enormous.
There are plenty of commercial targets downtown, hotels near Disneyland, and large massess of people to hit. AQ needs to hit California if they intend to draw us deeper into this conflict, and they know it.