The CS admit rate for Cal Poly SLO is around 6%. Tougher than the majority of the UC’s. You are looking at an average of 4.21 GPA and 1481 SAT score for the College of Engineering and you can guarantee that the CS stats are higher than the average for the College of Engineering.
Also SLO does not accept Undeclared and trying to switch into CS/SE will be virtually impossible unless you are admitted into the Engineering college in the first place. SLO will allow major changes but one criteria is that you have to meet the admission threshold as a Freshman applicant in the first place so this avoids backdooring your way into a more competitive by initially applying for a less competitive major.
There is nothing wrong with UCR, UC Santa Cruz and the many Cal states for CS. Like I stated on your other thread, my younger son went to SDSU and landed a good paying job after graduating this past May as a Cybersecurity analyst.
Cal Poly Pomona, Cal State Fullerton, Cal State Long Beach and possibly San Diego State will all be good options for CS and you have a decent chance for an acceptance. You have to remember that employers are more interested in what job skill set you can bring rather than the name of the Diploma.
Again, I advise you to apply widely and you should have some good options in the end.