Do as well as you can in your college courses, since how well you do in college will be the biggest factor in transfer admission. UCs and CSUs generally take only junior level transfers, but your 2.9 HS GPA will not affect your application to them since you will have enough of a college record when you apply.
Here is some transfer admission information for UCs:
https://www.universityofcalifornia.edu/infocenter/transfers-major
SJSU transfer admission thresholds can be found here:
http://www.sjsu.edu/admissions/impaction/
Use http://www.assist.org to help you plan your courses to fulfill prerequisites for your intended majors and needed general education requirements.