Here is the actual code I use to resolve the initial need, this was taken for another question/answer an really works, the only thing I like to make is to put each position of the post of the column at the same row of the other term.
<?php
// for a given post type, return all
$post_type="evento";
$tax = 'categorias-eventos';
$tax_terms = get_terms($tax);
$post_counter = 0; // reset so we can generate columns
$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
if ($tax_terms) { ?>
<ul class="column_wrap" style="width:45%; float:left;">
<?php foreach ($tax_terms as $tax_term) {
$args = array(
'post_type' => $post_type,
"$tax" => $tax_term->slug,
'post_status' => 'publish',
'posts_per_page' => 6,
//'posts_per_page' => -1,
//'paged' => $paged,
'orderby' => 'title',
'order' => 'ASC',
'caller_get_posts' => 1
); // END $args
$my_query = null; // clear the query variable
$my_query = new WP_Query($args);
if( $my_query->have_posts() ) { ?>
<li class="column_row" style="float:left;">
<h4><?php echo $tax_term->name; ?></h4>
</li>
<?php while ($my_query->have_posts()) : $my_query->the_post(); ?>
<li class="column_row" style="float:left;">
<div class="retailer_wrap retailer_id-<?php the_ID(); ?>">
<p><strong><?php the_title(); ?></strong></p>
<p><?php echo get_post_meta($post->ID, 'eventdate', true);?></p>
<p><?php echo get_post_meta($post->ID, 'eventplace', true);?></p>
</div>
</li>
<?php $post_counter++; ?>
<?php if ( 0 == $post_counter % 6 ) { ?>
</ul>
<ul class="column_wrap noneed" style="width:45%; float:left;">
<?php } // END if $post_counter ?>
<?php
endwhile;
//wp_pagenavi( array( 'query' => $my_query ) );
} // END if have_posts loop
wp_reset_query();
} // END foreach $tax_terms ?>
</ul>
<?php } // END if $tax_terms
?>
This is a graphical example of what I like to make:
<div class="term-row">
<div class="col1"><h4>Term 1</h4></div>
<div class="col2"><h4>Term 2</h4></div>
</div>
<div class="even-row">
<div class="col1"> // here begins the 1st post of the 1st term
<?php the_title(); ?>
<?php the_excerpt(); ?>
</div>
<div class="col2"> // here begins the 1st post of the 2nd term
<?php the_title(); ?>
<?php the_excerpt(); ?>
</div>
</div>
<div class="odd-row">
<div class="col1"> // here begins the 2nd post of the 1st term
<?php the_title(); ?>
<?php the_excerpt(); ?>
</div>
<div class="col2"> // here begins the 2nd post of the 2nd term
<?php the_title(); ?>
<?php the_excerpt(); ?>
</div>
</div>
<div class="even-row">
<div class="col1"> // here begins the 3rd post of the 1st term
<?php the_title(); ?>
<?php the_excerpt(); ?>
</div>
<div class="col2"> // here begins the 3rd post of the 2nd term
<?php the_title(); ?>
<?php the_excerpt(); ?>
</div>
</div>
<div class="pagination">
<a href="#">Prev</a>
<span class="current">1</span>
<a href="#">2</a>
<a href="#">Next</a>
</div>
Hope its clear enought 🙂