Tried the pupusas at the Donut Field in Mountain View Friday night. The Donut Field is, ostensibly, a donut shop, although it also offers ice cream. During the day, after the morning crew has made the donuts, they offer El Salvadorian food -- pupusas being chief among their offerings.
I ordered an assortment of four pupusas on Friday. The wait was about 15 minutes, despite the "comida rapida" sign, but I just sat around reading a copy of the Metro. Other options would be playing the video games they have installed or munching donuts and ice cream.
The wait was pretty much worth it. I got four very large pupusas, piping hot. Really piping hot. Impatiently grabbing one before the plate had been sitting more than a couple of seconds, I had to drop the crispy disc faster than you can say "Ay, Caramba". These are freshly prepared, with your choice of stuffings (pork, cheese, beans, or combination thereof -- no loroco, however). Served with the pupusas was a serviceable commercial grade salsa and an insipid curtido (Tu Casa Salvadorena's is much better). Put together and eaten like a taco, the combination was perfectly satisfying. In fact, I regretted ordering 4 pupusas, because they were large enough to fill me up after the third one. Perhaps I shouldn't have had those donut holes....
Anyhow, the Donut Hole can be found next to the Cost Plus World Market at 1910 W. El Camino Real.