When will Jacksonville grow up. There's a million+ people in this area, granted many of them have no desire to go downtown. If a food truck is what it takes to get people down there, it's not taking someone who otherwise would have been coming to your brick and mortar store, but it's adding vibrancy and activating an otherwise desolate area.
If someone sees a food truck and thinks, hmm, this food looks a lot more appealling than your restaurant, you are doing something wrong with your restaurant. Compete or fail, because America.