I would use a completely separate device for that purpose, and use it on an open wifi or only turn it on with mobile connection to effect the transfer, then turn it off immediately.
One thing I would like to add is that places with open wifi usually have security cameras and you don't want to be caught on video tapping away on your laptop complete with timestamps. You should therefore use your device discretely - try to use it from the public toilet if the signal reaches there. Also wear a disguise as you enter or leave the location.