How is the UCD environment? I was thinking of applying, going into a biology major. How are the dorms, the city, and the atmosphere? Is it pretty safe and/or friendly?
Following since I’m also curious. Plan to visit but would like to hear experiences from current or former students. 
It’s a true small cow town haha. A little isolated, but that also means it’s a very calm and serene campus. The dorms are eh. They’re college dorms. Small, but they get by. They are constantly adding new dorms (they just added 3 new dorm buildings I believe in Tercero) which are really nice. The city and downtown are all chill. A lot of friendly people, it’s a true college town with lots of small theatres, tiny shops and eateries.
Is it friendly? Yes. Everyone claims the best thing UCD is known for is the friendly faces. It’s true. There will always be those kids who are competetive, but most are willing to make connections.
Safe? Very, compared to other UC campuses. My friends get regular campus police warnings from UCLA and UCB about robberies, sexual assault, etc. We get very few warnings here. I think the last time we got a campus police report (something that happened on or near campus) was when a person was stealing people’s mail. But it is a large college campus in a town. It’s safe, but stuff still happens.
All in all, a pretty calm atmosphere to study at. You can get bored!
Based on the colleges we visited last year, UCD’s dorms are nicer and more spacious than many other UCs. The dorms include a desk, dresser, bed (that can be set at three different heights), a chair and a desk lamp. Tercero has the new dorms and they are adding onto Cuarto this year. Segundo is your traditional long hall dorm. Cuarto is suite style and technically off campus (across the street from campus).
Check out Aggie Abodes for videos showing various UC Davis dorms. http://housing.ucdavis.edu/aggie-abodes/