I started off as engineering, intending to go into EECS. You are given 40 hours of studying a week, be prepared to sacrifice sleep, socializing, fun things. You will find that Engineering is quite different than other majors and things going on campus, I would say take it seriously and be very independent, self-motivated, and don't rely on help to be given. A lot of students here know how to game the system and get good grades, be prepared for a major deflating of your ego and I would say don't try to stand out. You will get 30s/100s on exams, they will be curved. Math classes and science classes will be hard first two years, SERIOUSLY, to make it at Cal, you have to be one huge ASSHOLE. That's good advice, to put up with a lot of GSIs, fellow students,
Crowded lectures, lines at the RSF, and . DONT DO ANYTHING DIFFERENT, wear the same clothes as everyone else, don't ask questions, Cal doesn't like people who ruffle up feathers, you're going to have to deal with a lot of hierarchy and bureaucracy here, a lot of time you see things are not indicative of ability, but ability to BS and navigate resources, win social approval, dress nice, be good looking, and athletic. That will win you points, don't smoke.
If you want girls, you have to be tall, good-looking, rich, and thin. If you are in Engineering, forget about it. I would say get that degree and focus on making money, seriously you are wasting your time trying to find a girl at Cal, wrong school. You have to be memorizing content, solving problems, doing problem-sets, that the next thing on your mind is to eat or sleep after 48 hours. Do things for yourself and don't rely on other people. Expect people to be rude and douchey big time at parties or even playing sports, I'll be honest Cal is very elitist, students from very rich families, high socioeconomic status, priviledged. If it doesn't seem like a cultural fit, you're going to suffer. There are some cool, open-minded friendly people now and then, but very self-absorbed and status-seeking in my personal opinion. You wont make much conversations out of the blue, and this is discouraged even.
People that come to Cal are focused on the prestige and want to get a job at Google, Goldman Sachs, McKinsey. Or to a medical school or good law school.
I don't know if people come here on this board to rant or if they had bad experiences, the "losers" of Cal. Oh yeah, and there are a lot of gay people here, no offense.
Focus on getting a good GPA (which is hard), securing research, and internships.
If your family has money, a private school would be better off for you.