Applying for UCLA’s Tap program is not going to do anything with your chance of getting into UCSD. UCLA’s Tap program is solely for UCLA. UCSD will not look into that at all. That being said, the good news for you is that UCSD does have its own “tag” program called UniversityLink with participating community colleges in the San Diego area. I’m honestly not familiar with the program and how it necessarily works, but check it out if you are eligible for it! Link is provided down below 