Indeed, if your website is on joomla 1.7 you won't be able to use joomfish until they release a compatible version. They are actually working on one and have a first development version available, although it is still hard to use if you're not a developer. There is also the falang extension which is a port of joomfish onto 1.7 but that extension is also in beta so it might require some tweaks to make it work.
In that case, you can use the joomla 1.7 multi language system, but it's a lot less practical than with joomfish:
you need to create several category trees, one per language.
Then, in each category trees, you need to create duplicates of products, one per language, attached to the corresponding category for the language of the product.
Then, when you create your menus and modules, you can restrict them to one language, and set the corresponding category in the "parent category" option of the menu/module.
Or you could also make your website with Joomla 1.5