My understanding is that UCSD admits to the university first, so if you do not get in to the CS major, you may still be admitted. I have heard of many students being admitted undeclared. So I’m glad you applied for CS there, since that gives you a chance to get in to the major, with a fallback option built in! (I was concerned that you might have applied for Math-CS primary. Math-CS majors have more limited access to CS classes and it might not really be the major you want.)
UCSB also admits to the university first and then the major. And I am not as familiar with UCI admissions, but I think they might do that, too.
For UCD, I have read here on CC that occasionally they admit to the alternate major… but we have seen a lot of CS applicants from our high school, and it seems anecdotally they are either admitted, denied, or waitlisted… not admitted undeclared or to an alternate. Since the admit rate for the CS major at UCD is in a similar range to UCI / UCSB / UCSD, I would consider it to be similar to the others in likelihood (rather than Likely, as you might expect from the overall admit rate).
Good luck, the UCs can be unpredictable but I expect you’ll have some good options in the end! 
