Just fyi:
I called my department at UCLA on March 31 and they told me that a decision had not been made yet--but by the afternoon, I received an email directly from the Chair of the department that stated that I had been accepted to UCLA and will be mailed the other information soon. The online admissions site where you were told to check for decision status still said that my application was still under review (hadn't been updated since Dec.). However, since the email from the Chair, I am assuming that the website status is now null and void for me.
As for USC,the last time I called was last week and initially the lady gave me the general "we are sending out decisions through March 31 by post only". Then when I was transferred to the financial department (for a different question), the person who answered said that USC had made a decision about my application and I should receive the letter by post this week. Nothing more than that.
So, I'm guessing, calling is not bad. We'll see what happens with USC.