I beg to differ about the coffee, which I rather like (at least from decent cafes). Not quite Milan, but better than US or Canada and certainly London.
As for writing, I adhere to the 8-hours-a-day, 5-days-a-week, at your desk school of writing (from Woody Allen and James Mitchener, no less), with an occasional break for a shot of whiskey. But Poesia is nice. There are lotsd big, old style cafes that have good wifi and dark corners to hide in.
Personally I like real isolation. I just spent 3 months finishing my third book of non-fiction. I went to Salta and lived at a scientific research centre up in the mountains. Sadly, I was robbed on the way back to BA and lost the last 1/4 of my manuscript and am busy trying to re-create it even as I flesh out my next effort.
If you want to hook up for a coffee and commiserate about stupid editors, in a gfew weeks I will have some time. I am in Olivos, but go downtown sveral times a week.
Good luck with the book.