http://www.ucsd.edu/catalog/curric/PHYS-ug.html indicates that for the typical BS physics major at UCSD, there are three upper division restricted electives to be applied to the major, but you would still have schedule space for non-major electives (and possibly additional general education courses, depending on which UCSD college you enter). The suggested schedules list 2-3 physics major courses for each of the six quarters in your (after transfer) junior and senior years. This leaves space for 1-3 other courses each quarter that you can use for out-of-major electives like economics, CS, etc. courses.