Multilanguage support

I am currently trying Hikashop for a client. I am using Joomla 2.5.6.

I read in the documentation that for multi-languages you use Joomfish.

I have successfully built several multilingual sites (English/French) using Joomla 1.5.

To my knowledge Joomish is not yet ready for Joomla 2.5 (A source of great frustation since I would like to migrate my current clients!

My question how do you do that? Would I have to install Hikashop on Joomla 1.5 in order to be bilingual? If so how would I migrate

You can use Falang on Joomla 2.5.
It's a port of JoomFish for Joomla 2.5

For new websites, you should definitely start with Joomla 2.5.
Joomla 1.5 support by the Joomla team will end soon.