The San Jose Mercury New ran a review of the Los Tapatios Taco Truck a while back, and I finally stopped to try it myself. You may still be able to find a cached version of the review via Google. I'm no taco truck expert, but these did seem very nicely made and were quite yummy. I ordered 3 tacos: al pastor, carne asada, and lengua. The fillings were generous and the meat was tender and flavorful. The lengua had green tomatillo salsa on it which complimented the meat nicely.The plate came with a slice of lime (just one, which might not be enough for some people), plus a large radish slice and a bunch of pickled jalapeno slices. No prices posted, but 3 tacos + 1 largish bottle of water came to $5.25. There are a few rustic benches and a rustic table at which to enjoy your food and a splendid view of 101 traffic rushing by below.
Los Tapatios Taco Truck
On Old Oakland Road between 13th and 880 (or Gish, if you prefer)