2.6 GPA high school to a UC

If you start at a community college, http://www.assist.org will be your friend in course planning.

For example, here is its listing of Los Angeles Pierce College courses to take for major preparation for mechanical engineering at UCI:

http://web2.assist.org/web-assist/report.do?agreement=aa&reportPath=REPORT_2&reportScript=Rep2.pl&event=19&dir=1&sia=LAPC&ria=UCI&ia=LAPC&oia=UCI&aay=16-17&ay=16-17&dora=MECH.ENGR

UCI general education is listed here:

http://web2.assist.org/web-assist/report.do?agreement=aa&reportPath=REPORT_2&reportScript=Rep2.pl&event=21&dir=1&sia=LAPC&ria=UCI&ia=LAPC&oia=UCI&aay=16-17&ay=16-17&dora=GE

You may also complete IGETC in lieu of general education for most majors at most UCs and CSUs.

Note that you must also satisfy base transfer requirements described here:

http://admission.universityofcalifornia.edu/transfer/preparing-admission/minimum-requirements/index.html