The earlier report is very informative, just wanted to add a few quick notes.
You can check the Preserves web page at http://www.cosumnes.org/
Check the Activities link for a monthly Guided Paddle from March thru October weather permitting. It is an excellent opportunity to learn from the volunteers about the preserve and wildlife as well as meet other like minded paddlers.
There were 12 people in our group all from different locations in Northern California. All different age groups can handle this laid back adventure. Be warned it is about a 200 yard haul from the parking lot to the launch dock, so bring your cart if you have, if not they have a couple of Wheeleez donated by California Canoe and Kayak they will be happy to let you use.
Everyone was very friendly and helpful. At this time we ran into a little current at one point where the river narrows, maybe a knot and a half. Everyone easily handled it. It was unseasonably hot though, 90 degrees this day. Make sure you bring plenty of water and snacks. Not to mention PFD's, paddles, and rudders if so equipped for inflatables. One couple had forgot their rudder for an inflatable kayak, since they don't track as well it can make for a more strenuous paddle in current. Watch for snags though, this is an undammed river with fallen trees just under the muddy waters. I got teed up on a flat log face sticking straight up about 3 inches under water. Never saw it, next thing I know I feel it underneath me and it was holding me tight in mid-stream. I managed to paddle off it though. All in all a fun paddle.
Nice accommodations, bathroom at parking lot. Even though the entrance to the parking lot is gated, you can exit at anytime so don't worry about being locked in!
No Fees or permits required.
From Sacramento: Take I-5 South to Twin Cities Road, go east turn right on Franklin Blvd. Look for signs about a mile up on the left. Can't miss it! Check the website for more directions and maps.
They have a paddle map online you print up or pickup at the visitor center.