Life is a grand adventure for Stargirl. It is full of mystery, wonder, and excitement. She tries new things, she learns new things, and she is full of zest. And when Leo begins to join her on her adventures, he, too, begins to get a bit of that zest. He starts noticing a lot of things around him that he never really paid attention to before because they were so common. For these two, even the most mundane locales, like, say, a shopping mall, are meant to be explored. And that exploration doesn't always have to be physical; it can be mental, too. In Stargirl, both Leo and Stargirl, along with many of the other characters, explore new ideas and knowledge and are better off for their journey.
Stargirl's explorations into other people's lives only get her into trouble and bring others pain. She should do a little less exploring and a little more minding her own beeswax.
Stargirl shows us that we should view all the world as a place to explore, even the less exciting parts. After all, a random spot in the desert can be enchanted.