So apparently there is only one Mexican restaurant supplier that only has the blue Pepsi menu board with the white letters, photo board with taco/burrito combo with rice and beans shots, and horchata/jamaica drink fountain because it's awfully strange that Roberto's has the same setup and I can remember these things back in various locations in SoCal.
Appearance aside, I was able to get a decent two taco combo here for seven bucks with rice and beans, and 3 rolled tacos with guac for another three bucks. The shells were nice and crispy like I like them and there was a sufficient amount of marinated shredded beef. Areas where Fausto's and Roberto's differ are hot sauce, Fausto's is spicier and tomatoier, Roberto's is open 24 hours, Fausto's till 11:45 they say.
So which one do you go with? I'd say by whichever you're closer to, but Fausto's might have the edge if it isn't 2 am, as I like spicier sauce and I have had random "gifts" in my food at Roberto's before.