Translate Membership Level Names with Paid Memberships Pro

my_init_membership_level_translate.php

/*
	Filter membership level names for translating.
	
	Add this code to a custom plugin or your active theme's functions.php file.
	
	Be sure to update the $pmpro_translated_level_names array. Add a sub array for each locale.
	The sub array keys should be the membership level ids, and values should be translated membership names.
*/
//defining translated level names.
global $pmpro_translated_level_names;
$pmpro_translated_level_names['es_ES'] = array(
	1 => "Primero Nivel",
	2 => "Segundo Nivel"
);

//filter pmpro_levels global
function my_init_membership_level_translate()
{
	global $pmpro_translated_level_names;
	
	if(empty($pmpro_translated_level_names))
		return;
		
	$site_locale = get_locale();
	
	foreach($pmpro_translated_level_names as $locale => $level_names)
	{
		if($locale == $site_locale)
		{	
			global $pmpro_levels;
			$pmpro_levels = pmpro_getAllLevels(true, true);
			
			//translate
			foreach($level_names as $level_id => $name)
				if(!empty($pmpro_levels[$level_id]))
					$pmpro_levels[$level_id]->name = $name;
		}
	}
}
add_action('init', 'my_init_membership_level_translate', 1);

//filter levels page
function my_pmpro_levels_array($levels)
{
	global $pmpro_translated_level_names;
	
	if(empty($pmpro_translated_level_names))
		return;
		
	$site_locale = get_locale();
	
	foreach($pmpro_translated_level_names as $locale => $level_names)
	{
		if($locale == $site_locale)
		{			
			//translate
			foreach($level_names as $level_id => $name)
				if(!empty($levels[$level_id]))
					$levels[$level_id]->name = $name;
		}
	}	

	return $levels;
}
add_filter('pmpro_levels_array', 'my_pmpro_levels_array');

//filter checkout level
function my_pmpro_checkout_level_translate($level)
{
	global $pmpro_translated_level_names;
	
	if(empty($pmpro_translated_level_names))
		return $level;
	
	$site_locale = get_locale();
	
	foreach($pmpro_translated_level_names as $locale => $level_names)
	{
		if($locale == $site_locale)
		{
			if(!empty($level_names[$level->id]))
			{
				$new_name = $level_names[$level->id];
				$level->name = $new_name;
			}
		}
	}
	
	return $level;
}
add_filter('pmpro_checkout_level', 'my_pmpro_checkout_level_translate');

//fix current user's level
function my_pmpro_after_set_current_user_translate()
{
	global $current_user, $pmpro_translated_level_names;
		
	if(empty($pmpro_translated_level_names) || empty($current_user->membership_level))
		return;
	
	$site_locale = get_locale();
	
	foreach($pmpro_translated_level_names as $locale => $level_names)
	{
		if($locale == $site_locale)
		{
			if(!empty($level_names[$current_user->membership_level->id]))
			{
				$new_name = $level_names[$current_user->membership_level->id];
				$current_user->membership_level->name = $new_name;
			}
		}
	}
}
add_action('pmpro_after_set_current_user', 'my_pmpro_after_set_current_user_translate');

An updated version that also translated descriptions can be found here: https://gist.github.com/ideadude/0ddfa9b9e4f313f4f08c2c55a41f8441