I don't think I'm fluent in Latin, but...

When I went to translate some words into Latin, it asked me to verify that I was either native or fluent in Latin. I'm far from either, especially as it's not really a spoken language, but I feel I could give an accurate translation. I've taken four years of high school and two semesters of college latin, and I think I can manage some simple English to Latin.

How serious is the fluency restriction on dead languages?

Yes, you're right, it's an automatic text that is not very well suited for dead languages. I think you can do the English to Latin without any problems