When to go
All months are suitable to photograph from behind the HOLLYWOOD sign, but I think the best sunsets happen during the winter, when lots of clouds are in the weather system.
Check for promising conditions if you're looking for a cloudy sunset like in my photo. April is probably best for temperature and scenery, since the flowers and plants are in full bloom by then.
Sunset is best from this location, as the sun is setting to the west and away from Downtown Los Angeles. Sunrise is tough, because you'll be shooting towards the sun.
Field tips
Do not go past the sign - security will catch you immediately! Respect the laws.
Be prepared to hike about an hour to get to this spot.
A wide angle-lens (16mm) is your only bet to get the entire sign in one photo. Shooting landscape is your best bet and you can crop later.
You can aim towards downtown like in my composition or you could aim towards the right and capture Lake Hollywood with the Pacific ocean in the far distance.
I recommend holding your camera as high up as you can to get the best vantage point of the sign beyond the fence.
Try to catch some golden light on the hills or over the city before the sun drops too low.
Current weather
Los Angeles, California
Clear
Do nearby
There are lots of hiking trails nearby. You can access the Wisdom Tree and even Griffith Observatory from trails that connect from this viewpoint.
Sunset Ranch is a small horse farm that offers horsehides around Griffith Park, if you're up for an adventure like that!