The following countries are currently supported in the Store Locator Plus plugin. These countries determine the default center starting point for location searches and determine which Google locations engine is used when searching for an address. This influences, but does not restrict, which results are returned. Regardless of what country you select as the default, any location in your location database can be returned by the search regardless of the country in which that location resides. This does not effect the zip codes necessarily. Some country postal codes are unique, others are not.
The following findings are current as of WPML 3.4.0 and SLP 4.5.07.
The short version: When using WPML to switch languages you will want to make sure your alternate language files are up-to-date and installed in the Store Locator Plus languages folder. You can use Loco Translate to sync and generate updated .po/.mo files. Also check out the WordPress Translate for Store Locator Plus site and download the latest .po and .mo files from there.
Store Locator Plus sets most of the default text in the Text Manager class using gettext functions. When a page implements the [slplus] shortcode the string presented in various locations, the default Find Button label, for example, is NOT loaded in the alternate language despite using the WPML String Translation plugin.
Manually setting the translation via the WPML String Translation admin interface does not seem to to be used by default despite WPML Multilingual CMS, WPML String Translation, and WPML Translation Management being installed and active.
Using Loco Translate To Help WPML
By using Loco Translate to sync and save an updated .po/.mo language file to the SLP languages directory, the WPML language switcher will now pick up the proper translation. The process I used to get the Italian translation for “Find Locations” to show up when I select the Italian version of the page:
Unlike single-language websites where all of the site content and administrative interfaces are operating under a single language, multilingual sites allow visitors to pick their language while viewing the website.
The most popular plugin for WordPress multilingual sites at the time of this writing is WPML.
Store Locator Plus has begun the journey into supporting multilingual sites with WPML. Changes to WPML in late 2015 will require further revisions to the WPML compatibility layers.
Since version 4.3.06 Store Locator Plus added features that will help the plugin and add-on packs communicate with WPML for user-configurable translation strings. While the entire fixed-text portion of Store Locator Plus uses gettext, a common language translation utility, there are many strings that appear as user-configurable settings. Options such as search and results labels fall into this category.