The American River Parkway is one of the best things about the Sacramento area. There is a bike trail from Folsom Lake to Old town. I have ridden it often over my 18 years in the area and it is always a treat. For the most part the trail hugs the banks, but there are a handful of stretches where you may ride up to a mile w/o seeing the river. In spite of this, riding the trail is always a great way to "get away" without having to travel too far.

I would also recommend you travel with a friend because some stretches are lesser traveled and a serious fall or injury could leave you isolated for some time. Always bring at least basic repair equipment. I would also recommend leak-proofing your tires as there are many goatheads (hard, sharp, seed pod type stickers) and you are bound to hit one. When I first started riding, I got half a dozen flats in one week before I discovered leak-proofing my tires.