“I’m using scholarships and loans for the rest.”
Scholarships are definitely not guaranteed until you have the letter in hand. The best scholarships usually come from the university that you attend. As such, where you attend will have a huge impact on what scholarships you are likely to receive.
By the way, one daughter has a merit based scholarship that requires that she maintain a 3.5 GPA in university to keep the scholarship. While she is doing so with some to spare, this would certainly not be a guarantee for many students if they needed the scholarship to afford the school. Some merit scholarships require the student to maintain a GPA which is not quite this high.
Loans are not free money. They have to be repaid with interest. Having significant student loans will significantly impact where you can work. For example some students end up having to live with their parents after graduation in order to save money to pay off loans. This has a huge impact on where a new graduate can find a job. However, finding an appropriate job can be quite challenging right after graduation, even for students with pragmatic sensible majors such as engineering.
My daughter who graduated about two months ago was thinking about taking loans before she went to university. I however pretty much forbade her to take loans. Now she is very glad that she has no debt upon graduation. Her first job is enough to pay the bills, but living on her own (in an apartment shared with a friend) would be very tight or not possible if she also had loans to repay.
“…good safety schools since I have close to a 75% chance of getting in”
If you have a 75% chance of getting into a very good university, then it is a very sensible place to apply, and a very likely place for you to attend. However, it is not a safety. It is a match (and IMHO two very good ones in this case).
“any school I look at I prefer the admissions rate to be below 50%.”
With a 3.6 weighted aiming for an engineering major?
One piece of good news is that California has very good in-state options.
To be fair, I do expect you to get into good in-state options where you can do very well. You also have a very sensible major which should lead to a good job after graduation. I am just being a bit picky with regard to how you might want to think about where to apply.