Not really.
Even if you have an open network you still need to give it an SSID or tell it to scan for open networks and then attach.
There are a few examples of scanning for networks to identify signal strength and type of connection.
You could modify that to attach to the strongest open one.
I am sure there are examples on the net or you could ask in the more specific ESP groups.
Here is a link that may be of interest to you
That looks at doing similar to what you want.