A Visitor can be seen on the rooftop (top left side) of Little Future.
The Goobacks' written language is seen. It is actually ASCII, a way of representing characters on computers. Specifically, their language is the extended ASCII characters 179 to 218, which are single and double lines that can be put together to draw boxes.
At the '"they took our jobs" meeting one guy suggests increasing global warming to trigger another ice age. In the late 1990s, reputedly, paleontologists held that at the begining of the last glaciation England went from 5 degrees warmer than today to being under a half mile of ice in about 100 years.
"Gooback" is a play on "wetback", a disparaging term for those who have illegally crossed the border from Mexico to the US.
There is a route 285 in Colorado, but it is a US highway instead of an interstate. There is an Interstate I-285 - it is the beltway (or ring road) that encircles Atlanta, Georgia.