17.5% of the students at UCSD are international, in addition to the 5.5% that come from out of state. And remember, California is a very large, populous state, so it’s not as if the California kids are all in big cliques that already know each other. My son knew only one or two kids from his Northern Californian high school who also attend UC San Diego. So, everyone will be trying to meet new people when they arrive as first year students. And I don’t think you need to worry about people thinking you might be too “different” because you are from Illinois. We Californians have grown up with so many people whose families have moved to California from all over the country and all over the world., so some little differences of backgrounds, cultures or perspectives are totally normal among peers.
That said, it could be helpful to join a club or do a team sport as a way to help you meet other students in smaller group settings. UCSD first year class sizes are typically very large (with smaller discussion sessions), so it might be easier to get to know students while doing things other than just attending classes. The dorms are, of course, one place where students get familiar early on with a good number of other students.
UCSD does have “Outreach Coordinators for International and Out-of-State Students.” You can find out more about the support services they offer by visiting heir web page:
http://thecolleges.ucsd.edu/nonresidentinfo/index.html. The only thing I know about them is that they organized a traditional Thanksgiving dinner for students who live too far away to travel home for the four day weekend. The Thanksgiving meal was just $5 and there was also a service project that students could do together that afternoon. I thought that was a nice event so students who couldn’t travel home wouldn’t be alone on what is traditionally a very family-centered holiday.