If the parish has a website, it'd probably be best to look at that for info about what they expect, since there can be significant variety among Orthodox. That being said, if it's Antiochian, I can almost garuntee you that the service would be in English. There aren't many Middle-Eastern Americans who are also Orthodox Christian outside of Detroit, so most are very convert-oriented. Because of this, they tend not to get up-tight about lack of experience with the liturgy, since many in the congregation started in the same place. Of course, this could be all wrong, so your best bet would be to go and see what happens. The Frederica link should serve as a good guideline.