Locales Ruby on Rails issue

I have a issue with Locales.

In rails app /config/locales/ I have two files: cs.rb & en.yml

my index.html.erb looks

<% if notice %>
<p id="notice" ><%= notice %></p>
<% end %> 

<h1>Zoznam produktov</h1>

<% @products.each do |product| %>
  <div class="entry" >
    <%= image_tag(product.image_url) %>
    <h3><%= product.title %></h3>
    <%= sanitize(product.description) %>
    <div class="price_line" > 
      <span class="price">
        <%= number_to_currency(product.price, :locale => :cs) %>
 %>
      </span>       
    </div>
  </div>
<% end %>

At the end, the output of price is in $, I really don't understand why.

Thanks.