This is basically a movie about two teenagers on the run. They meet for the first time. The girl is streetwise and assertive. The boy is geeky and naive. They drive off through an America with lots of great scenery, and there's humour and romance and some feel good music. This is what is at the heart of the movie and it works well.
What doesn't work well is the back story, about the boy being born on mars. It makes for a pretty uneven film that starts out as a sci-fi movie with a crew of astronauts heading out to the stars, then morphs into something completely different. The special effects in space are wasted, because this part of the story didn't really need to be shown. Plus, some of the incidental music doesn't work too well.
The makers should've just stuck to the story of a lost boy who wanted to see the world, and a girl who just didn't fit in and was willing to show it to him.
