Mystified? The alphabet itself is a naive casting of English phonemes into a parallel set of symbols. A "may be encryption method" that remains "unbroken" is better described as a matter of sheer speculation. Absence of evidence is not proof of presence. I'd like to credit Dee & Kelley with otherworldly communication, but I don't know that the language as such bears such inference.
A good point, helped by the fact that the 'communication' was never finished IIRC.
It's almost amusing that opinion seems to be almost split right down the middle with this subject, with some believing every word written and others saying that Kelly simply told Dee what he wanted to hear - it's certainly true that just about everything Kelly 'revealed' was available to him in Dee's library, but this entire theory stands or falls on exactly how much Dee himself saw & heard in the sessions. His diaries do not make it absolutely clear, but it does seem that Dee himself saw & heard more than has been widely admitted.
Enochian as a language? Possible, but so far not proved (although none of the Grimoires have ever been 'proved' either but given the muddled versions that appeared in the Mediaeval period & then the Renaissance afterwards perhaps it's not surprising considering that no 2 'translations' of the Key of Solomon, or the Goetia, or the Sworn Book of Honorius - hell, any of them really - agree with each other, but again I digress......)
Communication with non-human entities? Also possible but again not proven, although Dee's diaries are the closest to proof we have ever seen assuming that Dee was not simply being gullible of course (which is often claimed these days) but I would venture to say that whilst Dee desperately wanted to believe (he could be said to have been the Fox Mulder of his time) he was still - regardless of the detractions by his undoubted enemies - the most intelligent & cleverest man alive at the time.
He would also have been all too aware of the dangers of coming right out with what he wanted to say in plain language, which leads me nicely to the idea of encryption - this was something Dee excelled at (remember always he was a talented mathematician and well versed in the Pythagorean school of thought as well as a very accomplished Geometer and the possibility of hidden encryptions in his writing is extremely plausible.
The trick to understanding Dee is to understand the way he thought and careful study of his Monas Heiroglyphica (in both the original Latin as well as English) will bear some very tasty fruit indeed (okay, I stretched that metaphor somewhat but you'll have to forgive me as I am a huge fan of Dee and his work).
I can highly recommend the work of Jim Egan in understanding the Monas - please let me know if you would like some of his books uploaded here.