One of the hidden Mickey’s at Mulholland Madness is located on a billboard near the entrance queue.  Look out for a swimming pool in the shape of a hidden mickey.  It’s right next above a sign that says "Alamo Rent A Car" and below a house with a tennis court.

Here is a picture of the Mulholland Madness Pool Hidden Mickey.

There are a few hidden Mickeys at the Mulholland Madness roller coaster at Disney’s California Adventure. 

if you look on the billboards at the entrance of the ride you will find a California license plate that says "ADVNTUR".  If you look closely at the tab on the license you will see a small black classic hidden Mickey.

Below is a picture of the license plate hidden Mickey on the billboard near the entrance queue at Mulholland Madness.

There is a Hidden Mickey on Toy Story Midway Mania at the loading dock for the ride.  If you look at the wall on the backside of the loading dock you will see a three toy story characters in circles.  The circle with Jessie makes the head while the circles with Bullseye and Rex make the ears.

Below is a picture of the Toy Story Mania Hidden Mickey formed from Jessie, Bullseye, and Rex.

As you ride Monsters Inc at Disney’s California Adventure pay attention to the control panel toward the end of the ride.

There will be all sorts of buttons, levers, and switches.  Towards the center of the control panel you will see a turn dial and two circular gadgets above it that form a classic Hidden Mickey.

Below is a picture of the control panel on the Monsters Inc ride with the hidden mickey.

Inside the building of the Monsters Inc ride at Disney’s California Adventure there is a poster on the wall that says "Monstropolis" with a picture of a yellow cab. 

If you look at the headlights of the cab you will notice a classic upside-down hidden mickey.

Below is a picture of the Monsters Inc hidden mickey.

As you exit the Tower of Terror you will arrive in a store.  Go over to the photo picture counter and you will see shelves on each side of the counter,  On the shelves you will see some old fashion cameras.  If you look closely at the face of some of the cameras you can see a classic Mickey formed from the lens of the camera and two circles above it.

This is listed in the Disneyland’s Hidden Mickeys book under California Adventure clue number 9.

I personally feel this one is a bit of a stretch, but some of them could be a Hidden Mickey.