Bro, go wherever you will feel most comfortable. It is not worth it to go to Cal if you feel like you will have a low GPA. A high GPA from UCSB will > Low GPA from Cal. Go wherever you feel you will succeed the most. Congrats on getting in on Cal.
Hope you can decide and remember even though Cal would be more competitive than UCSB, it might motivate you more to do better and you might end up surprising yourself.