I know how you feel because I also went to Cal Poly SLO for undergrad. You have nothing to worry about! Like shingamiasuka mentioned, the success of your graduate application mainly depends on what you did and how you performed at school. I can assure you that you have a fair chance of getting into any of the top 10 engineering school as long as you have a relatively competitive application (GPA, GRE score, LORs, SOP, etc.). Keep in mind that I only applied to Master's programs. Just to give you a little more background, I applied and got into the MS programs of the following schools: Stanford (EE), Duke (Bioe), UPenn (Bioe), UMich (Bioe), Georgia Tech (EE), USC (Bioe), and UCLA (Bioe).
Good luck!