Although there are a couple of trips in the story, to Vegas and across the country, the main setting for His Robot Girlfriend is southern California. Mike lives at 11 North Willow street Springdale, California 82803. Springdale is a fictional town. I thought it sounded as though it could be in California. I looked in the Zip code book to find an unused zip code number which would fall in California and used it.
Mike's daugher Harriet live in Greendale, a nearby town. It too is fictional. I was imagining the drive to my mother's house. She lives in the area of our city known as Green Valley. Or at least she lives near it.
In the story, Mike and Patience go shopping at the mall in Pico Mundo, another nearby town. This was an homage to Dean Koontz and his very excellent book Odd Thomas. Odd Thomas lives in the California town of Pico Mundo, and the mall there plays an important part in that story. If you haven't read the book, you should.