Random suggestions:
- Temecula wine country, about 40 miles south.
- Apple picking and "fall harvest" atmosphere in Oak Glen near Redlands.
- Small but interesting air museum at March AFB in Riverside. Also the Planes of Fame Museum in Chino, about 10 miles west.
- Drive up to Arrowhead and/or Big Bear, there could be snow by then.
If you let us know your likes and dislikes there may be more focused suggestions. Also browse Trip Advisor for Riverside "Things to Do" as well as the forums.