When I was studying "La vallee des cloches" from Miroirs, I used the Schirmer edition, as it was the only one I had in my music library at the time. I've never been too high on Schirmer, but it worked fine in that instance. I note in Hinson's repertoire guide that the choices for Miroirs are Max Eschig, E. B. Marks (I found their sheet music for the "Pavane pour une infante defunte" dreadful, including poor print quality and missing notes), Schirmer, Schott, and Kalmus. (Kalmus generally has endured considerable criticism over the years, but seems to have improved more recently.) And, evidently, "Alborado" is printed separately by International Music as well. Their editions are usually excellent, a fine example being their Complete Brahms. If you will only being studying Alborado you might try International Music first. If you will be studying other pieces in Miroirs, then maybe look for Eschig (as long as it's unedited) with Schirmer as a fallback, as it seems to be an ok edition in this case. Good luck with this piece!