I think anonymous access to samba is only working if all pc's are in the same workgroup / domain. So that's no option.
The way I use it, i have anonymous access to samba disabled.
Then when I connect with my corporate laptop (which is joined to a domain), I get prompted for a username and password.
You can also create an extra user on your router, with the same username/password you use on your laptop. This way it should connect to the share without prompting for a username/password.