Whether to Use Real or Fictional Towns and Zip Codes

One thing that seemed inevitable in the wake of Trump saying pets were being eaten in Springfield was memes and videos of The Simpsons, the long-running animated comedy set in a fictional town known as Springfield. It's never been said exactly where Springfield is, even though several U.S. cities bear the Springfield name.

I don't want to mention a lot about the Orange Menace (this is a topic I like to avoid). But as I said, the Simpsons references seemed inevitable after his recent claim. And the fact that The Simpsons is set in a fictional city also brought to mind something I recently did when I began writing my newest work-in-progress. 

I was uncertain about using my own home town and zip code in a fake letter I used as part of my WIP. I immediately made up a city name, Holtsville, and at first, I did use the actual zip code for Hollister, California, but after reading a comment on this post about my work, I decided to check for a possible zip code that might not exist. The actual zip code for Hollister is 95023 (95024 for P.O. Box addresses). I tried 95025, and saw that it's not an actual zip code. So I used that in my fake letter. 

The Kinsey Millhone books (A is for Alibi, etc.) are set in a fictional town, Santa Teresa (based on Santa Barbara, CA). The books reference the fictional University of California campus at Santa Teresa (referencing the real-life UC Santa Barbara).

Though The Simpsons setting of Springfield is not in any specific state,  at least one fake zip code has been used (on Homer's drivers license), although the article says the zip code is that of Kalamazoo, Michigan (This is in fact true).  And one episode made reference to another iconic Fox series, Beverly Hills 90210, spoofed as Springfield Heights 90210. This, even though 90210 is the actual zip code for Beverly Hills. References like these make the location even more of a mystery.

Also, in the letter in my WIP: the letter is from a hospital, a fictional name of which is also being used. I chose the generic-sounding Holtsville Community Hospital on Sunrise Drive (a reference to an actual street in my town known as Sunset Drive). I glanced through my copy of this book, and saw letters from a  hotel in Chicago. The zip code used in the letter is an actual Chicago zip code. But a search for the hotel name, Hotel Wintercourt, produced no results for a real-life hotel of that name, though links to the book appeared.

Have any of you used fake city names and/or zip codes in your works?