Agile Store Locator has the option to choose the language using which the map should appear, the option can be selected under the ASL Settings > Maps tab.
In the Map Language field, a two-character language code is required such as fr, de, pl, etc which must in a small code, the country code can be seen from here.
The above code will only change the language of Google Maps and not the complete widget, the widget translation is available in the Store Locator translation guide.
In case you have multiple maps on different pages, each widget can have its own language through the shortcode attribute.
[ASL_STORELOCATOR map_language="de"]