I'm in a Mac and Windows environment and the libraries for a Windows pc are in the same folder as the application, but on a Mac they are not.
This isn't entirely correct.
Mac, Windows, and Linux have a "libraries" folder for the libraries included with the Arduino IDE. That's what you see when you unzip on Windows. On Mac this folder is inside the Arduino.app bundle.
This is not the location for user contributed libraries.
The correct place for user contributed libraries on all three operating systems is the "libraries" folder inside of your "sketchbook" folder. The reason you want user-contributed libraries here is that when you upgrade to a newer version of the IDE, the libraries you added won't be affected by the change.
Your sketchbook folder is defined in preferences. So you can just point your sketchbook folder to a folder inside your Dropbox folder.