It looks as if the jury remains out on whether Einstein ever endorsed astrology if I may quote from Robert Todd Carroll's "Skeptic's Dictionary:
April 18, 2000. I received an e-mail today from Ivan Kelly, renowned expert and critic of astrology, regarding a widespread claim among astrologers that Albert Einstein once wrote: "Astrology is a science in itself and contains an illuminating body of knowledge. It taught me many things and I am greatly indebted to it."

Ivan contacted Geoffrey Dean, another renowned expert and critic of astrology, who wrote the following:

Dear Ivan,   Re that Einstein quote. This is a good example of astrologers quoting each other nth hand, but with nobody ever checking the original quote.

In a letter in Correlation June 1991, 11(1):35-36, I chased it back to a book (in French) by the late Swiss-Canadian astrologer Werner Hirsig, Manuel d'astrologie, where the quote appears in French in the preface, but with no source given. From there it was quoted by Solange de Mailly Nesle (1981), from which it was quoted by Tad Mann (1987) and Percy Seymour (1988), and from there ever onwards seemingly without end.

The Hirsig book ends with a postscript dated February 1950, so the quotation must date from before that time (Einstein died in 1955). Hirsig's widow did not inherit his papers, so she was unable to check them to see if they gave the source. Various people including Solange, Percy and myself have checked Einstein's writings and biographies but have been unable to verify it, so Solange and Percy have deleted it from later editions of their books. His biographies contain nothing to suggest Einstein had any interest in astrology, and its style differs from that of authentic Einstein sayings.

My letter ended "Accordingly, until the quote is authenticated, it should be ignored lest it add to the blight generated by Newton-Halley, Evangeline Adams, and other famous-but-wrong quotes."

Hope this helps.

Regards, Geoffrey
Oddly, Google doesn't seem to be able to come up with any reference to the quote that isn't on an astrology site or debating its authenticity. Which is odd, given that almost every pronouncement of the old goat is recorded copiously all over the web.
Stephen Hawking has his own views on astrology. Shall we put him down as a "maybe" then?