Get the GPS coordinates of a photo in Mac Photos.app
I just tested exporting a file from Photos and it retained GPS information. Are you using Export > Export X Photo(s), or Export > Export Unmodified Originals for X Photo(s)? I used the latter.
To find the actual GPS coordinates there are many, many solutions, but I used the most-excellent command line ExifTool when testing to ensure the GPS information was still present after export.
$ exiftool -gpslatitude -gpslongitude ~/Desktop/IMG_9337.jpg
GPS Latitude : 41 deg 2' 14.99" N
GPS Longitude : 90 deg 8' 38.55" W
There are many things you can do with this, including scanning an entire directory and outputting their GPS coords to a file, outputting into HTML format, etc. The above command will give you a basic display of it, though.
Right click on the photo and choose edit with Preview. Go to Tools → Show location info
and click on the GPS tag.