Ralph's truck runs by my office in north Scottsdale almost every afternoon. NOTHING can beat the the convenience factor, instead of spending 15 minutes fighting airpark traffic to buy a crappy burger, I just roll out to the back of my building and order some fresh tacos.
The prices are pretty decent and the food quality is good (but look, it's still got a fast food element to it so we aren't talking gourmet but it's pretty decent!)
The cook and the driver are SUPER NICE and always have a great attitude when I see them.
If you see them driving around, flag them down for some yummies! :)