Hubcapsc...
The Los Angeles Forest has various approaches to reach the "crest." I always start on the east side.
It begins just about five miles up the road from my home. From my driveway to the very top of Mount Wilson is just 29 miles.
http://en.wikipedia.org/wiki/Angeles_Crest_HighwayYes, the Sierra Madres are one of several groups of mountains that cluster around the Los Angeles Forest.
That route approaches the crest from the south. The route is heaven to dirt vehicles of all kinds.

CA #2 / Angeles Crest Highway (in my photos) runs for about 65 miles.
It gets more beautiful as you continue east through ever changing landscapes...

I'd say that significant reductions in air pollution are most helpful to reforestation and beauty.
When I moved to this area back in '74, one could cut the smog w/a knife! ??? It was awful.
These days one hardly hears warnings about smog levels. Most of what one sees these days is "marine layer,"
which many people mistakes it as smog.

Los Angeles City and County are a flat desert.
The Los Angeles Forest is the first group of mountains away from the Pacific Ocean ('bout 35 miles)...
All the marine layer and/or smog backs up against these mountains...
When that happens, you hop on the Valk and leave it all behind.

Rain around here is a rare commodity... when it does rain for a couple of days the air cleans up
and you can see the Pacific Ocean from Mount Wilson.
NOTE: Three years ago it rained on 4 July for about 1/2 hour... a first in 70 years!
The photo I show of the LA basin, on a clear day would allow one to see several cities with the ocean as a backdrop.
FOR THOSE WANTING TO VACATION IN SoCal.The following locations are within 500 miles from my home in Glendale, 91206: ???
1. Hollywood and all its attractions... (8 miles away);
2. Universal Studios-Hollywood... (7 miles away);
3. Burbank Studios... Jay Leno, etc... free tickets (6 miles away);
4. Downtown Los Angeles... (8 miles away);
5. Los Angeles Dodgers' Stadium... (5 miles away);
6. Venice Beach... (22 miles away - West);
7. Pacific Coast Hwy/Malibu ... (25 miles away - West);
8. The Pasadena Rose's Parade ... (6 miles away);
9. The Rose Bowl... (4.5 miles away - East);
10. Magic Mountain... (20 miles away - North);
11. Disneyland... (35 miles away - South);
12. Griffith Park / Griffith Observatory / L. A. Zoo / Western Heritage Museum... (5 miles away);
13. The L. A. forum (home of the Lakers)... (18 miles away - West);
14. Staples Center... (8 miles away);
15. San Diego Zoo... (150 miles away - South);
16. The Mexican Border... (180 miles away - South);
17. Santa Monica Beach... (25 miles away - West);
18. Santa Barbara... (65 miles away - North-West);
19. The "Sunset Strip..." 10 miles away);
20. San Francisco- coastal route #1... (425 miles away - North).
21. Las Vegas - Desert route (no choice) ... (270 miles - East).
If I was visiting here on a thight budget and did not know anybody, I would motel it out
100 miles away... East; a lot less expensive... and near other attractions.
Excellent freeways and by-ways.
RECOMMENDED PERIOD: To ride on T-Shirt, early April through late October is good...
June is the ugliest month! Always gloomy. August and September are the hottest months... ride shirtless!

"When you don't know where you are going any road will take you there."