I can't find the thread, but I seem to recall that someone said roaming data is required for audio guides rented at historic .
Am I remembering that correctly? We're trying to decide if we just bite the bullet, get Verizon's month of international use and be done with it, or the $10/day.
If you rent (or receive as part of the entry ticket) a physical audioguide, the information will already be on it. However, a lot of museums have shifted to downloadable material you access on your own phone. Frequently you start by scanning a smartcode. There's nearly always supposed to be WiFi in those museums, but in my experience it doesn't always work well, so getting the desire material can be iffy. I've also had several less-than-perfect experiences with museum-supplied audioguide devices that are supposed to sense where you are and start playing the correct audio. I don't know what causes that type of problem.
You might take a splitter that allows two people to listen to the audio from a single device.