I lived in San Diego for 14 years, and was a member of the BMW Owners club of San Diego.
On their Web site, there is a map of the area, with lots of good roads graded and noted. You can print it out. http://www.bmwocsd.org/
You need more than three days!
The club meets on Saturday and Sunday mornings at Giovanni's restaurant for breakfast, and rides after. Click on the EVENTS button for details. Saturday rides tend to be quite fast and technical. Sunday rides can be varied. Usually more than one group will leave for a ride on Sunday, ask around for the type you want to take, fast and technical, or slower and scenic.
If I still lived there, I could take you on an ALL DAY ride, twisty and scenic, very little highway, and not see the same place twice. It would be hard to find a better riding area in the US!
You MUST do the Palomar Mountain, East Grade is sweeping turns, South Grade will give you a real workout!