De Anza College classroom PE12U is on the upper level of building PE1.
At the map linked to below, you can find classroom PE12U most easily by first finding the swimming pools, the light blue square and rectangle at almost the center of the campus:
To go from the swimming pools to PE 12U, the doors/gates between PE buildings PE1 and PE2 are sometimes locked from the outside but have bars you can push on from the inside (pool side) to get out. See buildings PE1 and PE2 at the map above or this closeup map:
In the upper right hand corner of the PE1 building in the close-up map you can see the numbers 12L and 12U. 12L is downstairs and 12U is upstairs at that side of the building, (the north side, facing towards the Forum building).
Here is a photo of the entrance door taken from just outside the PE1 building.
(Ooooops, the tiny yellow letters in the photo above that you can barely read are where the door is.)