The UCSC campus is up on a hill a little bit away from town, so off-campus housing is going to be pretty much equally far away from all departments on campus. It's about a 3-minute drive from the base of campus (which is surrounded by a nice residential neighborhood) to campus proper, and practically every bus in town goes up the hill to campus. You get to ride any city bus for free as a UCSC student, which is cool.
You're probably going to want to look for housing on the Westside or near downtown, because these are really close to campus. However, they'll be a little more expensive - about $700/month for your own bedroom in a shared house on the Westside is pretty typical. I currently live in a 2-bedroom duplex about a mile from campus, and the rent is $1600/month. If you plan to drive to school or don't mind a longer bike/bus ride, it is probably worth it to check out housing east of downtown and around the Live Oak area, which tends to be a bit cheaper. It is VERY doable to get around Santa Cruz without a car, and I recommend it, as parking on campus is wicked expensive. Santa Cruz is a very bike-friendly city.
Craigslist is a great resource for finding housing in Santa Cruz, but be careful and start looking well ahead of time. I've definitely met some sketchy people on there, and have had some people completely flake out on me, once even after agreeing that I could move in. But, I also found the wonderful house I live in now, and the wonderful housemate I live with.
If you have any other questions about housing or anything else, please feel free to ask! I love living in Santa Cruz and am very happy to share what I know about it.
