DO NOT buy carne asada from El Toro meats.. They will charge you $9.00+ per pound and it will be along the lines of what you get from Henry's.
There are a couple places where you can get CA locally.. One is at El Campeon in SJC. It's located at the NW corner of Del Obispo and Camino Capistrano, in the Union Bank shopping center. The second place is located at the NE corner of Alicia and Paseo de Valencia. It's back in the NE corner of the center, on the same side as the 7-11.
As for making your own.. All it takes is some OJ, sliced onions, cilantro, sliced limes, seasoned salts, pepper, garlic powder and onion powder. You can add some red pepper flakes or some other pepper power (chile powder, NOT chili powder).