Разобрался.
сделал тупо:
location @x_www {
internal;
include /etc/nginx/fastcgi_params;
fastcgi_index index.php;
fastcgi_param HTTP_REFERER $http_referer;
fastcgi_param HTTP_X_FORWARDED_FOR $proxy_add_x_forwarded_for;
fastcgi_param SCRIPT_FILENAME /var/www/rm/htdocs/index.php;
fastcgi_pass php_local;
}

location @static {
internal;
root /var/www/site/htdocs/;
}

location / { try_files @x_www; }

location /i/ { try_files @static; }
location /js/ { try_files @static; }
location /css/ { try_files @static; }
location /data/ { try_files @static; }