I have learned that October 12 is a holiday in Spain. Does anyone know how this impacts travels and sights and museums there? Thanks!
I haven't been in Spain in October, but I think the safest thing to do with regard to the museum/attraction situation is to check each sight's website. Usually it will list the holidays on which the sight will be closed. That's also an opportunity to see what the opening hours are, and whether there's any news of importance to you--a special exhibition, or an indication that part or all of the museum is closed for renovation or the like.
It will be some time before October train schedules are available, at which point I'd head straight to Renfe.com. Perhaps one of our Spanish posters can make a general comment about what to expect on October 12.
Oct 12th is the National Day of Spain (Fiesta Nacional de España), this is a public holiday so everyone has the day off. This means many locals will be traveling around Spain for the long holiday, a bit like what happens in the 4th of July in USA, so you may want to secure AVE/AVLO train tickets beforehand. Outside of the touristy zones you may find some smaller shops/restaurants closed, but not too many. Public transport runs normally. Hrs for major museums and tourist sites should not be affected, thought you may find an uptick of visitors to these sites on the 12th, as locals have the day off. Also depending on the city you are in there may be some patriotic events that could restrict access in city centers, the largest example being the grand military parade that goes through central Madrid.