Personalmente prefiero utilizar Wordpress en ingles, la versión original, pero claro alguno de los inconvenientes es que por ejemplo las fechas se encuentran en ingles, pero esto tiene un sencilla solución.

Para traducir las fechas de ingles a español en wordpress lo único que tenemos que hacer es traducir el archivo locale.php que se encuentra en el directorio /wp-includes de wordpress. Yo ya lo he traducido, y os dejo el código después del salto.

[COPIAR]
Código PHP (Copiar):
  1. <?php
  2.  
  3. // Date and Time
  4.  
  5. class WP_Locale {
  6.     var $weekday;
  7.     var $weekday_initial;
  8.     var $weekday_abbrev;
  9.  
  10.     var $month;
  11.     var $month_abbrev;
  12.  
  13.     var $meridiem;
  14.  
  15.     var $text_direction = 'ltr';
  16.     var $locale_vars = array('text_direction');
  17.  
  18.     function init() {
  19.         // The Weekdays
  20.         $this->weekday[0] = __('Domingo');
  21.         $this->weekday[1] = __('Lunes');
  22.         $this->weekday[2] = __('Martes');
  23.         $this->weekday[3] = __('Miércoles');
  24.         $this->weekday[4] = __('Jueves');
  25.         $this->weekday[5] = __('Viernes');
  26.         $this->weekday[6] = __('Sábado');
  27.  
  28.         // The first letter of each day.  The _%day%_initial suffix is a hack to make
  29.         // sure the day initials are unique.
  30.         $this->weekday_initial[__('Domingo')]    = __('D_Domingo_initial');
  31.         $this->weekday_initial[__('Lunes')]    = __('L_Lunes_initial');
  32.         $this->weekday_initial[__('Martes')]   = __('M_Martes_initial');
  33.         $this->weekday_initial[__('Miércoles')] = __('X_Miércoles_initial');
  34.         $this->weekday_initial[__('Jueves')]  = __('J_Jueves_initial');
  35.         $this->weekday_initial[__('Viernes')]    = __('V_Viernes_initial');
  36.         $this->weekday_initial[__('Sábado')]  = __('S_Sábado_initial');
  37.  
  38.         foreach ($this->weekday_initial as $weekday_ => $weekday_initial_) {
  39.             $this->weekday_initial[$weekday_] = preg_replace('/_.+_initial$/', '', $weekday_initial_);
  40.         }
  41.  
  42.         // Abbreviations for each day.
  43.         $this->weekday_abbrev[__('Domingo')]    = __('Dom');
  44.         $this->weekday_abbrev[__('Lunes')]    = __('Lun');
  45.         $this->weekday_abbrev[__('Martes')]   = __('Mar');
  46.         $this->weekday_abbrev[__('Miércoles')] = __('Mié');
  47.         $this->weekday_abbrev[__('Jueves')]  = __('Jue');
  48.         $this->weekday_abbrev[__('Viernes')]    = __('Vie');
  49.         $this->weekday_abbrev[__('Sábado')]  = __('Sáb');
  50.  
  51.         // The Months
  52.         $this->month['01'] = __('Enero');
  53.         $this->month['02'] = __('Febrero');
  54.         $this->month['03'] = __('Marzo');
  55.         $this->month['04'] = __('Abril');
  56.         $this->month['05'] = __('Mayo');
  57.         $this->month['06'] = __('Junio');
  58.         $this->month['07'] = __('Julio');
  59.         $this->month['08'] = __('Agosto');
  60.         $this->month['09'] = __('Septiembre');
  61.         $this->month['10'] = __('Octubre');
  62.         $this->month['11'] = __('Noviembre');
  63.         $this->month['12'] = __('Diciembre');
  64.  
  65.         // Abbreviations for each month. Uses the same hack as above to get around the
  66.         // 'May' duplication.
  67.         $this->month_abbrev[__('Enero')] = __('Ene_Enero_abbreviation');
  68.         $this->month_abbrev[__('Febrero')] = __('Feb_Febrero_abbreviation');
  69.         $this->month_abbrev[__('Marzo')] = __('Mar_Marzo_abbreviation');
  70.         $this->month_abbrev[__('Abril')] = __('Abr_Abril_abbreviation');
  71.         $this->month_abbrev[__('Mayo')] = __('May_Mayo_abbreviation');
  72.         $this->month_abbrev[__('Junio')] = __('Jun_Junio_abbreviation');
  73.         $this->month_abbrev[__('Julio')] = __('Jul_Julio_abbreviation');
  74.         $this->month_abbrev[__('Agosto')] = __('Ago_Agosto_abbreviation');
  75.         $this->month_abbrev[__('Septiembre')] = __('Sep_Septiembre_abbreviation');
  76.         $this->month_abbrev[__('Octubre')] = __('Oct_Octubre_abbreviation');
  77.         $this->month_abbrev[__('Noviembre')] = __('Nov_Noviembre_abbreviation');
  78.         $this->month_abbrev[__('Diciembre')] = __('Dic_Diciembre_abbreviation');
  79.  
  80.         foreach ($this->month_abbrev as $month_ => $month_abbrev_) {
  81.             $this->month_abbrev[$month_] = preg_replace('/_.+_abbreviation$/', '', $month_abbrev_);
  82.         }
  83.  
  84.         // The Meridiems
  85.         $this->meridiem['am'] = __('am');
  86.         $this->meridiem['pm'] = __('pm');
  87.         $this->meridiem['AM'] = __('AM');
  88.         $this->meridiem['PM'] = __('PM');
  89.  
  90.         // Numbers formatting
  91.         // See http://php.net/number_format
  92.  
  93.         $trans = _c('number_format_decimals|$decimals argument for http://php.net/number_format, default is 0');
  94.         $this->number_format['decimals'] = ('number_format_decimals' == $trans) ? 0 : $trans;
  95.  
  96.         $trans = _c('number_format_decimal_point|$dec_point argument for http://php.net/number_format, default is .');
  97.         $this->number_format['decimal_point'] = ('number_format_decimal_point' == $trans) ? '.' : $trans;
  98.  
  99.         $trans = _c('number_format_thousands_sep|$thousands_sep argument for http://php.net/number_format, default is ,');
  100.         $this->number_format['thousands_sep'] = ('number_format_thousands_sep' == $trans) ? ',' : $trans;
  101.  
  102.         // Import global locale vars set during inclusion of $locale.php.
  103.         foreach ( $this->locale_vars as $var ) {
  104.             if ( isset($GLOBALS[$var]) )
  105.                 $this->$var = $GLOBALS[$var];
  106.         }
  107.  
  108.     }
  109.  
  110.     function get_weekday($weekday_number) {
  111.         return $this->weekday[$weekday_number];
  112.     }
  113.  
  114.     function get_weekday_initial($weekday_name) {
  115.         return $this->weekday_initial[$weekday_name];
  116.     }
  117.  
  118.     function get_weekday_abbrev($weekday_name) {
  119.         return $this->weekday_abbrev[$weekday_name];
  120.     }
  121.  
  122.     function get_month($month_number) {
  123.         return $this->month[zeroise($month_number, 2)];
  124.     }
  125.  
  126.     function get_month_initial($month_name) {
  127.         return $this->month_initial[$month_name];
  128.     }
  129.  
  130.     function get_month_abbrev($month_name) {
  131.         return $this->month_abbrev[$month_name];
  132.     }
  133.  
  134.     function get_meridiem($meridiem) {
  135.         return $this->meridiem[$meridiem];
  136.     }
  137.  
  138.     // Global variables are deprecated. For backwards compatibility only.
  139.     function register_globals() {
  140.         $GLOBALS['weekday']         = $this->weekday;
  141.         $GLOBALS['weekday_initial'] = $this->weekday_initial;
  142.         $GLOBALS['weekday_abbrev']  = $this->weekday_abbrev;
  143.         $GLOBALS['month']           = $this->month;
  144.         $GLOBALS['month_abbrev']    = $this->month_abbrev;
  145.     }
  146.  
  147.     function WP_Locale() {
  148.         $this->init();
  149.         $this->register_globals();
  150.     }
  151. }
  152.  
  153. ?>