In a previous post, I stated that only UC Berkeley, Los Angeles, San Diego, and Merced use the personal statement in making an admissions decision. According to some recent information I found on the UC system website, the four campuses that use the personal statement in making an admissions decision are Berkeley, Los Angeles, Merced, and Irvine, not San Diego.
However, you should take your personal statement seriously, even if you are not applying to one of the four campuses mentioned above. Personal statements can be used in consideration for scholarships, and international students can apply for merit-based scholarships when they apply to the UC system.