To be honest, at this point in the cycle your chances probably aren't very high. AADSAS has already notified schools of people holding multiple deposits, and those students have been forced to decide on the school they want to attend - as a result there should be very limited movement on waitlists from this point on (only out of the ordinary circumstances would cause someone to change schools at this time - at least this is my understanding, somebody please correct me if I'm wrong). If you have another acceptance or live far away from UCLA (meaning you would have to pay to travel here for the interview), I would just not attend the interview but if UCLA is your absolute dream, you live close enough where the commute to the interview wont cost you anything or you dont have any other options at this point I'd go for it - the worst that happens is you won't get in, but the upside is huge!