Você tem várias meta_keys em uma coluna que você precisa de
IN() para meta_key e valor como meta_key IN( 'property_amount','property_land_type')
AND meta_value IN ('L','H','C',replace( replace(meta_value, ',', ''), '"', '' ) >= 1)
Tente esta consulta
SELECT wp_posts.*, wp_postmeta.meta_value FROM
wp_posts, wp_postmeta, wp_term_relationships, wp_terms
WHERE term_id = '12' AND term_taxonomy_id = '12' AND ID = post_id
AND ID = object_id AND post_type = 'property' AND post_status = 'publish'
AND meta_key IN( 'property_amount','property_land_type')
AND meta_value IN ('L','H','C',replace( replace(meta_value, ',', ''), '"', '' ) >= 1)
GROUP BY wp_posts.ID ORDER BY replace( replace(meta_value, ',', ''), '"', '' ) DESC
LIMIT 0, 10
EDITAR
Tente este com join , eu entrei no wp_postmeta duas vezes para duas meta_keys
SELECT wp.*, wpm1.meta_value AS `propert_type`,
wpm2.meta_value AS `property_amount`
FROM
wp_posts wp
LEFT JOIN wp_postmeta wpm1 ON (wp.ID = wpm1.post_id)
LEFT JOIN wp_postmeta wpm2 ON (wp.ID = wpm2.post_id)
INNER JOIN wp_term_relationships wptr ON (wp.ID = wptr.object_id)
INNER JOIN `wp_term_taxonomy` wptt ON (wptr.term_taxonomy_id = wptt.term_taxonomy_id)
INNER JOIN wp_terms wpt ON (wptt.term_id = wpt.term_id)
WHERE wpt.term_id = '12' AND wptr.term_taxonomy_id = '12'
AND wp.post_type = 'property' AND wp.post_status = 'publish'
AND wpm1.meta_key = 'property_land_type'
AND wpm2.meta_key = 'property_amount'
AND REPLACE( REPLACE(wpm2.meta_value, ',', ''), '"', '' ) >= 1
AND wpm1.meta_value IN ('L','H','C') AND wpm1.meta_value IS NOT NULL AND wpm2.meta_value IS NOT NULL
GROUP BY wp.ID ORDER BY REPLACE( REPLACE(wpm2.meta_value, ',', ''), '"', '' ) DESC
LIMIT 0, 10
