http://talk.qa.collegeconfidential.com/university-california-general/2127392-faq-uc-historical-frosh-admit-rates-by-hs-gpa-2018.html may help you with UCs. However, note that a popular major like CS will be more competitive than overall admit rates may suggest, and UCs tend to get more competitive each year.
http://talk.qa.collegeconfidential.com/what-my-chances/2095312-generic-chance-answer-for-super-selective-colleges.html may help you with Penn and Princeton.