Just a few minutes away from the beautiful Laguna Beach there is this trail (or better, a series of trails) going up and down the mountains, which makes for a really nice hike. There are trails that are quite easy and others that are a little more demanding, but it's still nothing that a reasonably fit amateur cannot do. The landscapes are beautiful, you really feel like you are getting away from the urban/suburban life of Southern California.
There are also rangers going constantly up and down, which makes you feel safe in case you get lost or need help.
If I may something that was not so cool, on the other hand, there a little too many mountain-bikers going downhill too fast for my taste. But all in all it makes for a great hike.