Utica reservoir is located near Bear Valley. It has a rocky wooded shoreline and many islands. Being forest service land, camping is allowed most any place that is not marked as no camping. There are a few islands that you can camp on, though the reservoir is also not that large, so it can be covered in a day by a strong paddler.
For more paddling near by, check out Spicer Reservoir and Union Reservoir. Spicer is the largest of the 3 (more than twice as large as Utica).
Power boats are not allowed on this reservoir (they are on Union Reservoir and on half of Spicer Reservoir).
There are pit toilets at some camp sites, but mostly this is primitive camping with little more than a fire ring built by a prior camper. None of the campsites are official, so all are first come first serve and do not require permits.
Fire permit may be required for camp fire. No other permit required to launch or camp.
Take highway 4 towards Bear Valley from the Central Valley. A few miles before Bear Valley, you will come to Spicer Reservoir Road (watch for the Sno-Park signs). Go down this about 5 miles until you see a forest road with a sign about Utica Reservoir. Take this. At the next intersection, you will see a sign for Union Reservoir to the right or Utica Reservoir to the left. Take the left and continue down until you see the reservoir.
US Forest Service
Map is available at http://www.fs.fed.us/r5/stanislaus/visitor/uticaunion.shtml