For the UC’s, they tend to be very GPA focused more so than test focused, but it really depends upon which UC’s you are targeting and your intended major. Top UC’s want to see a overall competitive application including SAT II subject test scores.
USC tends to be more test focused, so you definitely need to figure out a way to bump up your SAT score or try the ACT.
http://admission.usc.edu/wp-content/uploads/Freshman-Profile-2019.pdf
2018 Data:
25th - 75th percentiles for SAT:
UCB: 1360-1540
UCLA: 1340-1540
UCSD: 1300-1520
UCSB: 1270-1500
UCD: 1220-1480
UCI: 1230-1490
UCSC: 1210-1450
UCR: 1130-1380
UCM: 1020-1280
25th - 75th percentiles for ACT:
UCB: 30-35
UCLA: 31-35
UCSD: 28-34
UCSB: 28-34
UCD: 26-33
UCI: 26-33
UCSC: 26-32
UCR: 22-30
UCM: 19-26