I've not done any BBQ events, but I have done car shows, and I have found that the easiest people to deal with are smaller cities. Here in Dallas, I have worked with some of the suburban cities, and they have been pretty easy to deal with. Not all of them, but some. The ones that "get it" tend to be happy to help you out.
The problem I have encountered with state properties is that I am dealing with people 200 miles away who really don't care about what my event can do for the communities I want to set up in. On the other hand, local officials DO care about what the event could do for local business and community interests.
I haven't tried to deal with federal properties. I just assumed that it would be even worse than state properties.
Basically, city officials will sit down with me and hear what I have to say, and judge the event on it's merits. The higher you go on the government totem pole, the less interested they seem to be in the merits.
Private property can also be hard to secure for an event, as they are only interested in making money. And, they want to be guaranteed an income from the use of their property, even if it is an empty lot they've been trying to sell for 20 years. They see their property as being worth about 20 times more than it really is, and expect to get paid way too much for it's use.
That's just my experience.