How can I get into UCLA, Berkeley, or UCSD?

For UCSD, just have a decent weighted GPA (4.0+) and around 2000 SAT. Their admissions is very formulaic and is based on a points system. Looking at what you've said, I think you already have a good shot at UCSD. UCLA/Cal are a different story. You need to have a high GPA/SAT scores and extracurricular activities especially since you're aiming for engineering. I can't speak for UCLA but for Berkeley, the College of Engineering is the hardest college to get into. I don't think there is a GPA/SAT score that guarantees admissions into Berkeley/UCLA but I'd recommend you keep your GPA close to a 4.0 UNweighted and have an SAT score of 2100+.