I hope I have figured this out now, for anyone else confused and not reading the docs:-)
Without running docker-machine, then running docker, your machine is the host.
If you run docker-machine to create VM/droplet then run a container then your VM is the host. So if you want to mount files/directories from your local machine you must use docker-machine scp to copy over the files/directory to the VM then -v mount the files/dirs on the VM to a container.
To connect to your container back to your local machine which executed the docker-machine VM command, use the IP addr returned when running route to get the gateway of the VM !
from local host use
docker-machine ssh dev route | awk ‘/default/ { print $2 }’
But not working on the droplet VM I guess you still need to open up the ports for that.
Kinda makes sense once I worked it out but there must be a better way:-)