Bonita Lakes is actually a collection of three maintained reservoirs with a couple dams separating them from each other. There is a dirt path around the waters that you can bike, walk, run, or horseback ride. There are a couple loop options, so you can choose whether you want to go shorter or longer. These shaded trails are just outside of downtown and a great choice for getting into nature when you don't have time to drive a long way.
There are some singletrack trails on the west side of the lakes that you can get to from the main gravel trail, but most users stick to the lakes loop.