I'm not so sure about your chances-- I'm sure, being a CA state school, they prefer CA residents, but you must be good to have gotten an interview from out of state to begin with. If you're serious about UCD, definitely be ready to tell them why in your interview. Also, showing a commitment to CA and northern CA in particular definitely couldn't hurt.
How much time are you spending in Davis? I would definitely recommend spending some time walking around downtown, getting a feel for it. A great place to visit is Mishka's Cafe downtown, a popular study coffee shop (with lemon bars to die for!!). If you're around on a Saturday morning or a Wednesday evening, I definitely recommend checking out the local farmer's market. I think it's really fun!
You should hang out in the Memorial Union if you want to get a feel for the student body. Plus, a lot of the bus lines go to the MU, so you could hop on one of the buses and get a tour of the city. Go to unitrans.ucdavis.edu for their schedules. You should check out the different areas of Davis in case you need to look for housing.
Anyone know if the roses are in bloom over by Storer Hall and Briggs? That was really nice when I was an undergrad there.
You could also take a stroll at the arboretum, by Mrak hall. That's always pretty.