I can see the point of the set up taking too long as tear down only takes 2 weeks. The article says that they're trying to reduce set up times, and with some major investors involved, I can see it happening.
Having looked at Facebook, many people who live in the area have been able to actually drive right up to the circuit itself. Nothing in the island that normally is operational is shut down. So access isn't really restricted to begin with if some can get up to the track at this time.
Many of the environmental concerns are extremely ironic because the race area itself at dirtiest is cleaner than most parts of the island have been at cleanest up till recent. As I mentioned, the island used to be treated like a dump. Many parts of the island were so littered that just walking could be treated as playing a game of Minesweeper. In fact, the poor treatment by locals and visitors lead to access being banned at some points. Also, having attended race events, many spectators actually care about taking care of the facility, and I've seen several race events being cleaner than other events held at the same track.
Locating the race near the I-94 corridor is a bad idea since 94 is always busy, and with Romulus being where DTW airport is (the place is always busy with traffic because of that), traffic could potentially be exponentially worse than it already is. Also, the Detroit City Airport may not be viable as an alternative either because the airport itself is in limbo. Mayor Duggan and the city are looking at methods to either expand air service or shut down the airport entirely (city considered selling the airport during the bankruptcy). While the FAA won't let them do so at the moment, they could do so if they sold the land to another party. A lot of speculation says that most of the land will go towards building new factories if land is sold, and if such happens, the site won't work at all. Also worth noting that the US Customs operates out of the airport which will increase difficulty in doing anything with the land unless they relocate to another airport.