This park has really grown over the past few years. There are lots of trails - both paved and non-paved. It's fun to see so much water in the desert and water-type foliage. And you'll most likely see a lot of bunnies!
The trail I've run the most starts at Wetlands and goes all the way to Lake Las Vegas. It's a nice trail. Starts out pretty mild, but there are a lot of crazy hills as you go along. It's mostly used by cyclists - at least when I've been out there. Not sure I've actually ever seen another runner while I've run this trail.
There is also a really cool hidden canyon, carved out by the Las Vegas Wash. You can easily climb down into the canyon - just be sure to do it on a clear day. Wouldn't be very fun (or safe) during a flash flood.
The park is well maintained and there are restrooms within the park (but not out along the trail). The restrooms were clean every time I've had to use them. Parking is plentiful, too. I doubt you'd ever had an issue finding a place to park.