We've been here a few times and love it. So close to San Diego. Call to be sure the falls aren't dry. But even if they aren't running, you might find water snakes, salamanders, lizards and deer. You can jump and slide on the rock waterfalls, which are great when it is hot.
Beautiful stars! There are some great trails to give you different vanage points on surrounding mountains.
As for camping,there are really nice bathrooms and showers. Some camping spot are hilly so watch out as your tent area might have you sliding a little. Lots of flies in the heat unless you find a breezy area, like we did at the bottom of a hill under trees. Most spots have decent shaded areas. Check weather. Some nights can be chilly.
You can go to Julian for dinner/pie or the nearby lake is another great hike around or go up Mt. Laguna or down to the desert. Everything is relatively close.