I am making an application with a Google Maps on it, for Android. I have plenty of Markers on my screen and I am preparing customizable balloon for each marker when they are
You are not obligated to show title when you have it set, so you can use that and as long as you return a View from getInfoContents and not setText on any subview of that returned View with title value.
Depending on how and if you already keep references to all markers, there are alternatives, e.g. if you had List and List you can use a conditional if (policeMarkers.contains(marker)) { ... } else { ... }.
You can also keep a Map and do YourMarkerRelatedDataModel model = allMarkers.get(marker); and use that value to differentiate.
Finally you can use Android Maps Extensions, which adds functions like Marker.setData(Object) and Object Marker.getData() to keep your model close to your markers and not create things like Map.