Lem wrote in his journal:
"Na początku 48 roku wyjechałem na miesiąc do Pragi, gdzie zostałem zatrudniony w rządowej klinice im. Klimenta Woroszyłowa (wyobraźcie sobie u nas szpital imieniem Hermanna Goeringa). I ledwo wytrzymałem ten miesiąc. Codziennie jak nie masówka na stołówce, to agitka w szpitalnych garażach. W moim rodzimym krakowskim szpitalu na Montelupich byłoby to nie do pomyślenia. My byliśmy jednak najweselszym barakiem w obozie..."
"In the beginning of 1948 I went to Praga for a month, where I worked in government health clinic named after Kliment Woroshylov (imagine a hospital named after Goering in Poland). I barely managed to survive that month. Every day either a general meeting in the dining hall or political agitation in the hospital's garages. In Kraków Montelupi's hospital where I usually worked it would be unimaginable. We indeed are the merriest barrack in the [socialist] camp..."
Poles often called themselves that because censorship was the least strict there and we had some contact with the western culture (mainly through the "Kultura Paryska" - a Polish emigrants in Paris printed a newspaper that was very influential in Poland despite being theoretically banned - it was smuggled in en masse - it was so influential that to this day the political program developed by Giedroyć and Mieroszewski in that newspaper is serving as the core for Polish foreign policy - and it's working very well so far).
It changed depending on the period (50s were the worst) - but western culture was usually pretty well known and admired in communist Poland. We had very lively jazz scene, Beatles and other rock bands were played in radio (for example in Polish Radio 3 there were whole auditions based on showcasing western music - it was considered a "safety valve for Polish youth" by the communists).
We even had yearly indie punk/rock festival in Jarocin where all the anti-mainstream western-inspired kids went to drink and sing punk songs against the system.
Don't get me wrong - communism was obviously evil. But it wasn't competent/diligent enough to be 100% totalitarian in Poland. That would take too much effort and for what? You'd get paid the same either way. If you were unlucky you could definitely go to prison for a wrong joke or song. But most people didn't.
Anyway.
Lem definitely would have written that he liked American sci-fi if he did liked it.