Working with a group of non english speaking models and property owners.  What is the proper way to collect releases?  I assume each person would sign a release in their own languages.  But do I also ask them to sign an English version? Is that even legal for them to sign a release that they dont even understand? And would the agency accept non english releases?

iStock has a huge range of langages for MRs, which I found by googling 'istock model release languages':
https://contributors.gettyimages.com/article/7822?article_id=7822

Hopefully you can find the info for your other sites in the same way,