First time I lived in Spain was 1986-87, then 91-92, then 2000-2001. Now I go back pretty often and have spent long chunks of summers there. When I first went, as a college student, Ud./Uds. was used for anyone who was older than you (by more than a few years) and who you were just meeting. Things have gotten way less formal over the years, but I still use Ud. if someone (like hotel desk people) "Ud."s me first. And if I have to go into a bank for some transaction or something. Basically, for interactions that are of a business nature. But even there, if they "tu" (can't do accents on this screen) me first, then I use "tu" back to them. A few years ago, I saw an older hotel receptionist wince and grimmace when a student of mine addressed him as "tu." So I wouldn't say it's true that as a visitor you will never use it, but "tu" will be the form pilgrims use with other pilgrims. (Actually, if I encounter a fellow pilgrim, no matter what the person's age, who expects Ud. from me, I'll actually purposely not use it because that would violate the whole "we're all here on an equal footing" spirit of the Camino, and I'd be offended!) Also, vosotros IS widely used. I do a lot with the Central American population in the U.S., and they don't have that, so it's Uds. for everything. I STILL have to keep reminding myself to use Uds. with them because it doesn't feel natural to me. If you use Uds., Spaniards would certainly understand, and they're used to foreigners' Spanish. Most Spaniards are pretty gracious people. I think it's great, by the way, that you're trying to review your Spanish ahead of the trip there. I wish more people bothered, even just to get pronunciation of towns (and the Camino names!) right. It's a respect thing. Good for you.