I went to UCSB for undergrad and majored in chemistry. I lived in IV for 4 years and my gf lived downtown for a year so I have a feel for both. Honestly I would try to live downtown if you can. Goleta is cheaper yeah, but downtown is much nicer and fun (bars, warmer beaches), transportation is easy- you can take the 24x to campus for free and its only a 20 minute ride. As far as having your own room I am not sure. I think it'd cost about $1000 or so but I'd definitely start looking as soon as possible on craigslist because housing is tricky. I know people with pets that live downtown, its not impossible but will definitely make things harder.
I applied for this fall too and if I get accepted I will most definitely live in San Clemente for the first year (super nice rooms and I want to meet people), then probably live downtown in the following years. Cheers.