Short report for anyone researching in the future. :)
My friend and I ended up arriving in Valencia about 7:00 on Thursday evening and we caught the 7:15 train back to Barcelona on Friday evening. This turned out to be a highlight of our week and we were both so glad we made the effort!
The Fallas are hard to describe but so fun. Our apartment was north of the main square (normally a 10-15 min walk) and it ended up taking us an hour extra to walk it since we kept detouring a block or two to see more on the way from the station. There were lots of people out and about - a real carnival atmosphere!
After finally getting to the apt and checking in digitally, we headed out for dinner and started encountering the processions of bands and beautiful costumed children, girls, families processing the streets. At first we just followed the sounds. :) At some point we came upon part of the route and just stood and watched for an hour at least. After that, we popped in to an Italian restaurant on a main street (prices weren’t inflated for the festival) and enjoyed dinner and wine before heading off to late bed.
I won’t say we got the best sleep of our lives because of the constant fireworks explosions during the night but it was fine. :) We were there for the fun! Slept in the next morning and checked out at 11 for late breakfast and more festivities. Thanks, Avi, for the recommendation of the Granier bakery chain - it made a great breakfast! (We also ate at one the day before in Barcelona a block from Sagrada Familia.)
Then it was off to the cathedral area to see the gathering of the flowers - a big wooden Madonna with slats for fresh flowers brought by procession daily. And more bands and more processions! And more explosions. Ha!
We truly enjoyed it! And for us, one night was just right, although I might opt for a few extra hours on arrival day given a choice.
Other notes: before leaving Barcelona, I tried to make reservations for paella, but the recommended restaurant closest to the center was already full. So start early on this. And be sure to give the restaurant your order ahead of time - you may not be able to order paella just upon showing up, even with a reservation.
Valencia was a beautiful city center and we did not have time for it. I could spend a happy few days here with no festival.
There were a lot of people out and about but I heard very little American English - I kind of think most people were Spanish. There were definitely other European tourists, though.