Re-take SAT or take SAT Subjects for First Time (Attempting UCSD)

UC’s do not superscore. They take the best total score from a single sitting which would be 1990.
If your GPA is around 3.6, then UCSD/UCD/UCI and UCSB would be Reaches. Average GPA for all the UC’s except for UCSC/UCR/UCM is 4.0+ and UC’s are very GPA focused. Your SAT score is competitive for UCI/UCD/UCSB but a bit low for UCSD. I think your GPA will be more of a problem than your SAT. As stated in the above post, depending upon your major, SAT 2 subject test are recommended for usually the STEM majors, so I would consider retaking the SAT in October and try the SAT 2 subject test in November. You need to send them by December 2015.

http://admission.universityofcalifornia.edu/freshman/requirements/examination-requirement/SAT-subject-tests/index.html

Good Luck and hope you can pay the OOS costs for the UC’s $55K/year.