It appears that the current version of the nice one-click “Get current location” feature in the new WordPress.com editing system doesn’t work unless you have your wireless adapter turned on.
If it’s not turned on, there will be an error message stating “Can’t find current location.”
This issue has been tested and replicated a few times on an Apple MacBook Pro, but hasn’t been fully tested across multiple computers.
Hopefully this suggestion can help you.
Screen shots are below.
Below is the location widget.
Below is what happens if your wireless is turned off.
Below is what happens when the feature is working.
If you can’t get the feature to work, you can type in your location, or type in the relevant location. If your post is about an event or location relevant topic, then you may want to choose the appropriate location. Once you type in the location and press enter, you’ll get a map similar to the one shown above.