I really love this expression "nie ma nas w domu". So beautifil and funny
I guess an unwanted potential visitor could be calling your mobile phone, saying that they are in your area...
I disagree. The phrase "Let's say" CAN be hypothetical but at the same time what it simply means.
I think the context could be: "Oh, there's a salesman at the door." "Let's say we're not home."
OK, I understand. Still... it can have the same meaning of 'let's imagine', actually.
"Powiedzmy, że nie ma nas w domu. Kto wtedy da naszej córce jeść?" = "Let's say/imagine we're not at home. Who will then give our daughter something to eat?"
Interesting, but you have had to add a qualifying sentence to indicate the meaning. It is confusing. I would not expect the Polish to have the same (out of context) meaning as the English.
Is there not another way of saying it?
Well, but there's never any context, so if the sentence we have to translate, whether it's English or Polish, is ambiguous - the possible translations have to take all correct interpretations into account. So even if ommiting 'that' is incorrect in one context, it's correct in another one. Also, the version with "that" is the one that's displayed as the main one anyway.
Translating "Let's imagine" we have "Wyobraźmy sobie", there can be also "A co jeśli..." = "And what if...", there are definitely several ways to convey this message.
Just admit that you missed a point already.
Let's say that we are not home...
-...then who turns the light on? (glancing at the CCTV) -...who will mow our lawn? -...how will our pet named Steve survive?
No, because the the word pair 'Let's say' is usually used to indicate a hypothetical situation.. 'Let's say the weather improves. . . . 'Lets say you win the Lottery'. The phrase asks the person to imagine that they are not at home.
I do not think that was the (unlikely) meaning in the Polish.
Ok. . . it makes grammatical sense - but its not a grammatically correct translation of the Polish.