One of the Hidden Mickeys at Mulholland Madness is on the far side of the billboard at the entrance queue.  To see this hidden mickey you must look at the large billboard in the front from inside the queue.

If you look on the right side you will see a yellow car with a boy holding a red Mickey balloon.  Just above the balloon you will see a black classic mickey.  The right ear is cutoff the end of the billboard.

Here is a picture of the Mulholland Madness billboard hidden Mickey.

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.