In short, no.
In Project-GC mapping tools, the tool for measuring is in kilometres, regardless of the 'Use Imperial" setting in our settings. Not sure why.... If you would like them to change it then maybe log a "Project-GC support" help desk item
In the Geocaching web page, you can change the setting from Imperial/Metric in your preferences and this will then sort by your preferred measure. (https://www.geocaching.com/account/settings/preferences
). The Live Map lists both of course, metric above the line, imperial below.
The iPhone App is simliar, metric can be set on/off, in More->Settings. It is then used for everything.