Is the autorotation in San Andreas movie realistic?
Let's see how many things we can find wrong.  


There's a bang, smoke starts coming from the exhaust.  Master caution comes on and his first response is to tap and check the 115v AC gauge!  The pilot takes his hand off the collective!
You hear the engine wind down and the rotor RPM drop.  He announces a gearbox failure.  So why did the engine wind down?  His passenger even asks if he switched the engine off.  If the gearbox had seized, the engine would have been destroyed or, the input shaft would shear and the engine RPM would increase leading to a very rapid overspeed.  There is no gearbox failure mode that results in the engine winding down.
He had a long think and a bit of a chat after the engine and RRPM wind down.  In a Bell 412, with the speed of that wind down, the blades would have stalled after 2 or 3 seconds if he hadn't dropped the collective.
He announces that he is going to autorotate.  His passenger asks "auto what?"  He says we're going to crash.  The whole point of autorotation is that you don't crash.
With the RPM already low (let's forget that he would have stalled by now), his first action is to dive and you hear the RRPM increase.  In reality, they would go even lower.  If he wasn't already stalled (which of course he would have been) he would now.
He was straight and level, with significant airspeed over level open ground.  At the first bang and sound of the engine winding down, he would have lowered the collective and flared to preserve RRPM. He would then look for a good place to land, not a shopping centre car park, and fly towards it. 
Each time he flares, he pitches forward again and the RRPM drop rapidly.  Flaring like that in auto would cause a large increase in RRPM, possibly overspeeding and lowering the nose to the level would cause a small drop in RRPM.  Diving again would reduce the RRPM.  So why would you flare to increase, then dive to decrease?


In short, the sequence is complete nonsense.