If you like off-roading, seeing a little nature, 4-wheeling you probably know about Azusa Canyon. Take the 210 Freeway east to Azusa and head north. That's all. You head into the Angeles National Forest and pass the San Gabriel Dam. I've been up there a lot because I had a friend who did some 4-wheeling and had a sand rail. We stopped going there after a while because it got too crowded. But, it's the filthiest fun you'll ever have.
This picture is from my own personal archives and was taken at Azusa Canyon. There is always a little water there but right now there's a lot more water than usual, probably overflow from the damn after all the rain we had. Most times you can drive right under that bridge in the picture above. There is plenty of water everywhere and the mountains are beautiful and green, again after all the rain. It's a great time of the year to take a little drive and there are quite a few turn-offs as you head up the hill where you can stop and take pictures and more further up past the bridge where you can get out and take a look at the streams of water flowing down the mountains in the river beds.
Get out, take a drive and get some fresh air. Get out of the city and see what else Southern California has to see.