I want to apply Undecided, which I understand automatically puts me in the College of Letters, Arts and Sciences. I will definitely major in something within the College.
However, I am considering double majoring, with a second major either in Roski (intermedia), Cinema (Media Arts + Practice), or Annenberg (communication). Is it possible to declare this major later on, after I’m accepted? If so, when?
I tried Googling it, from which I could only gather that there is an application process. Is it highly selective? Would it be realistic to hope to be able to major in any of the aforementioned programs as well as in the College?
Can I indicate that I intend to double major in my application? How? What about an art portfolio; do I need one if I’m applying undecided?
Finally, how does this affect any merit aid I may receive? Would I be considered for more aid if I choose to apply to a different major, or if I submit a portfolio?
A big thank-you to anyone who takes the time out to answer my questions! 
I can answer part of your questions so will start there. Yes, you can choose to double major after you start, that is what most choosing to double major do. Some double and do it in 4 years no problem, it depends on how complimentary the majors are. However, a lot of students realize the work v. reward (possibly extra year of school and cost of tuition plus not working for that year, etc) of a double major and choose to minor instead, or even major/minor/minor. Doing a minor is easy in terms of “getting in” the program, you pretty much just talk to your advisor about doing it. My students there are business/accounting and engineering so I do not know about adding an arts type major on, I only know getting into those programs initially is like getting into med school - it is super competitive. But we chose USC because of the flexibility to move and change and add majors/minors, so I would rest assured that you can probably do almost anything you want to do if you work at it. Many many students decide and change after they get there so you are not alone! I know to get into Viterbi for example if you were adding it on after acceptance in attempt to change majors or double major, you have to have a certain GPA and meet certain requirements. I would guess same applies to all the schools there. Perhaps someone more familiar with these liberal art type majors can chime in. @Madbean and @Georgia Girl know their stuff! Good luck!
@CADREAMIN : Thanks for your input! I’m glad to hear that USC is flexible. I should’ve expected as much from a private school.
It would be great if anyone could elaborate!