SLO projection targets puts Psychology as a transfer at around a 4% acceptance rate while Child Development around a 9% acceptance rate so both pretty competitive.
For the best chances, you should have all required and desired courses completed by Spring 2018 along with a competitive GPA.
https://admissions.calpoly.edu/psy.html
https://admissions.calpoly.edu/cda.html
If you have completed all major Prep and GE’s, there is no reason to remain at SDSU if you plan to transfer however, what is your backup plan if not accepted to SLO? Also I would be careful in taking any upper division courses at SDSU, since SLO may not accept them for credit towards your degree.
I would consider going to Cuesta and then applying for transfer for better chances: http://www.cuesta.edu/student/servs_classes/transfer/CalPolySLO.html