Disneyland and DCA have a lot more decorations to put up for HalloweenTime than WDW does. But they wait for the public installation of the decor until the day after Labor Day. The Disneyland Half-Marathon is this weekend, so that's a busy time for the Resort anyway.
Disneyland Parking Structure Tram Route Halloween Vignettes
Disneyland Ticket Turnstiles at Halloween
Mickey Mouse Giant Pumpkin on Main Street USA
Dia De Los Muertos decor in Frontierland
Woody's Halloween Roudup at Big Thunder Ranch
What they did start on this week was the transformation of Haunted Mansion into Haunted Mansion Holiday that opens September 17th. That's a big job to decorate the mansion inside and out, and change out the ride show inside and add new animatronics and props. It's a total transformation, and it takes two weeks;
Haunted Mansion Holiday queue
HalloweenTime at the Disneyland Resort this year runs from September 17th until October 31st (Dia De Los Muertos decorations in Frontierland remain operating through November 2nd, per Mexican tradition)