mattia - 5:00 pm on Jan 16, 2012 (gmt 0)

Yes, you should definitely use different language in the URLs.
Our store is in english and in french and we have both french and english URLs.
I am not sure that all ecommerce platform will let you be multi-language at the URL level but the solution we use let us do it.
The solution we have also let us include the name of category on the URL, along with the product name so a product page URL will look like:

http://www.domain.com/category_name/product_name.html

make sure to have in each bottom page a link to the other language equivalent page.

best,
Marc

[edited by: lorax at 5:19 pm (utc) on Jan 16, 2012]