At this time, the only way to change the text is to "hack" the code.  A future release of the product will make this all configurable.  If you need to change the search URL, you may edit the googleapi.class.php file to make the change.  This file can be found in the joomla root/components/com_gmaps/classes folder. 

You will want to change line 342.   The action on the form specifically. 

This will be configurable in the next release.