First of all read this post. it will help a lot
nuevvo.com/blog/item/84-k2-inheritance-sub-templating
You need three new template overrides containing only the category_item.php file.
Once you have created them and assigned them you need to change this line of code and replace K2_READ_MORE with your language string.
<?php if ($this->item->params->get('catItemReadMore')): ?>
<!-- Item "read more..." link -->
<div class="catItemReadMore">
<a class="k2ReadMore" href="<?php echo $this->item->link; ?>">
<?php echo JText::_('K2_READ_MORE'); ?>
</a>
</div>
<?php endif; ?>
Repeat this task for each template.
