Hi, and welcome!
For any wild releases, you should be able to click on down to the individual books to see if there are specific details about the release location.
Sometimes there aren't; for example, the most recent BWI airport release was on Feb. 27, nearly a month ago, and the release notes only say "airport", so it's not really a book you could go hunting for very easily.
The release on the bus shows up as this release zone:http://www.bookcrossing.com/---/816116
That page shows that the release was made on March 24. If you click on the book's title, the release notes repeat the information in the release zone - the 8 am bus to NYC. Again, not easily huntable - but if you had happened to be on that bus and found the book, the release notes would tell you how it got there.
Other release notes have more explicit details, and if the books were left in fairly sheltered spots - book-swap shelves, Little Free Libraries, or less-obvious places like "hanging from a tree at the trail head of thus-and-such hiking trail" - they may still be there days or even weeks later, giving you a better chance to find one. But there are no guarantees, so if you want to go book-hunting, think of it as going fishing - try to enjoy the trip even if you don't catch anything! [Side note: I don't know how far you are from Rockville, but there's an active Little Free Library there that's well-stocked with BookCrossing books.]
If you haven't already done so, do read the site FAQ, and the "How to BookCross" page - both under the "information" tab. And if you'd like to see some examples of books that were caught, read the Site Watch forum; it can be reassuring, and may give you some ideas about where to release books of your own!