I love this park because you can just get lost--but you're never really too far from a parking lot. Even though the bikers are abundant, I've only had one negative encounter with a dude and I've been hiking here a few times a week for about a year.
As an off leash park, my dog loves that she can just run and run on the trails, chase animals (snakes most recently, need to curb that habit), and swim in the water. Though the water gets pretty low in the summer.
There are parts just challenging enough that you can do a good run and feel like you really worked out.
If you have a dog and live nearby, I'd make this a staple to your daily dog walks--it's more interesting than your neighborhood, more challenging for you, very beautiful, and of course, there's water for the pup.