Palomar
Palomar Mountain is a great place to go if you like the quiet peaceful atmosphere. There is a trail that leads from the Camp Grounds to the Observatory. That is not only beautiful but very entertaining with the natural wild life. Their curiosity peeks yours and so on.
As far as cost goes, I found that it was relatively inexpensive as well as, worth my time to go exploring and learning a little bit about nature and astronomy as well. The locals are friendly and helpful. All in all, I really enjoyed myself. My children had a great time learning on how the observatory was built, and the hike from the campground to the observatory was interesting too. We learned about the different plants and animals in their natural habitat.
This is a place that would greatly benefit you, if you are interested in hiking,nature and astronomy. It is also, a great place to take your children to go camping, hiking and fishing. There are many pull-outs along the way up to check out the awesome view of different cities on a clear day and night. For instance, on a clear night, you can see all the way to Catalina Island, or TJ and you can see on a clear day, all the way to the Ocean.