Of course, real human translation is the only way to translate something properly. However, if you can start with the machine translation, perhaps it would speed up the process.
Another way (in AutoHotKey pseudo-code):
Select text in Revit (in Text or schedule field)
Hit hotkey
Put text from Revit onto clipboard
Paste into Google Translate dialog and submit
Copy new foreign text to clipboard
Paste back into Revit (or paste into Design Review markup, or type both the English and the foreign text into a spreadsheet for further review).