The informal version given by JoeF can be found in slightly different form in the Digitrad: click
Vor der Kaserne, Amerikan Soldat
Mit viele Cigaretten und beaucoup Chocolat
Alles is prime; alles is gut
Nur zwanzig Marks fur ein' Minute
Noch einst, Lili Marlene, Noch einst, Lili marlene.
There must be made some corrections from the German point of view:
 prima (1st class, very good, number one) instead of prime
 Minut' (pronounce minoot, consider the rhyme to gut) instead of minute
 eins (one) instead of einst
Noch einst must be translated into once upon a time again which makes no sense, but the meaning of the line is another one, which is in German noch eins
In the Spiegel version the a before beaucoup must be omitted, it doesn't fit into the tune, and grammatically it makes no sense.
The orthography is not correct, but gives exactly the pronunciation of the American soldiers. (I have heard it all my life, since I grew up in a garrison town. Most famous GI I shook hands with was a certain Cpl Presley in 1958.)
There is a slight difference in both versions concerning the prices for Lili's services rendered. 20 Marks for only one minute seems a little bit high, even for these times. Maybe the old money before the currency reform in 1949 is referred to, but then any girl in her senses would have preferred cigarettes as the true (= black market) currency.
20 Marks (then about $ 5,-) for five (fumph = fünf) minutes seems a reasonable price and could fit the times after the currency reform in 1949, when the Deutsche Mark (now abandoned since January 1) made an end to the black market and took over from the cigarette.
If any former serviceman from the Ray Barracks should read this: Greetings from Friedberg! Barracks still standing, manned by our brave allies, and the King is unforgotten.