Hello, it's good to be concerned about duplicate content. After doing some searches I've found that Google is indexing both Spanish and English versions of the products. The English version typically appears first.
I've found that you are correctly using the rel=canonical tag to point to the original content source. This should relieve any worries you might have about duplicate content.
This is very good especially considering your products can be accessed from different URLs as in your example.
However, I would suggest you take a look at any Spanish language product pages that have 100% unique content to make sure the canonical is not pointing to the English version. This will hinder the search rankings for the Spanish version of the product if you want that to be ranked well.
Best of luck with your optimization efforts. If you have any questions feel free to respond.