Mi Gruillense experience
Last Saturday in the late afternoon I stopped at Mi Gruillense, having read the various installments of "Taco Trucks in Oakland." Unfortunately, my experience was not at all positive! I ordered 5 tacos to go: 3 carne asada and 2 al pastor. Some people were already waiting for their orders, but many more came AFTER I had ordered and paid. To make a long story a little shorter, I waited for at least 45 minutes, after EVERY OTHER person had been served. (I am NOT a young, perky Latina -- was that the problem?) Well, when I arrived home (about 5 minutes later) and opened the bag, I found that there were only FOUR tacos inside -- flabby, couldn't tell the difference between the carne asada and the pastor, and the beans were hard and undercooked. Also, the condiments and salsa I had requested had been omitted. Needless to say, I will not return to Mi Gruillense!
If you read the Taco Truck reports, though, you know that this truck is not very high on the list -- and I do remember the service was slow (although not that slow).
I wouldn't attribute any bad experience to your not being a "young, perky Latina," as I'm not one either, and I've never been served otherwise than strictly in the order my order was taken at any truck.
Finally, I'm a little confused by your comment about the beans being undercooked. Tacos don't have beans.