If you can edit the notes, I think that implies that you have access to the original files an not just PDFs. I think it's unethical to take working drawing files without permission but if the office gave its blessing then there is no issue... Although any architect should be able to read the detail without English notes.

I just have PDF files and all the notes and information on the title panel are in a foreign language. 

I thought about cropping the title panel out of the image and replacing the annotations in Photoshop but was unsure whether it would be frowned upon.

Leave as is and explain in title or text box if abs necessary. Don't change. As long as the drawings look good, nobody will read your annotations any way if it's for a portfolio and you can explain it all in person during interviews.

Yeah I wouldn't bother with it. We'll pick up on the graphic cues in the drawings anyway.

No. It exudes more authenticity and it would look good too ;)

I disagree with the above comments.

If handy, take a look at an issue of DETAIL (like the one below). It's very useful to have a translation specially for the materials used in the project specially if you have great technical experience. In this case it can be a legend similar to what DETAIL presents in their spreads.

Use it as an opportunity to explain your knowledge of the details during the interview. So, yes translate the annotations, but in person.