Translation:I could forget about a clean bed!
"As I walked into the lobby of the hotel, I saw it was dirty and had insects scurrying on the walls. I could forget about a clean bed!"
It's a weird sentence without context though.
It is always more difficult to figure out how to translate a sentence when the English is difficult to understand even when translated properly.
Based on the czech sentence, for me it's: Looking at the shabby entrance of the **hotel, you already knew what to expect from the interior: neither a clean hotel room nor a clean bathroom nor even a clean bed.
Makes sense. So in English, it might be, "You can forget about a clean bed!"
"On a clean bed I could forget"? Or would postel be declined differently then?
That sentence does not make sense in English -- unless you intend to say that, while you are lying on a clean bed, you are able to forget something unpleasant that you'd rather not remember. One of the Czech natives on the team can perhaps tell you if your suggested sentence could reasonably be understood from the Czech original.