That's an interesting point you make. Is the imperative form used with "nosotros" ever used in Spanish? Would you say "Lavemonos las manos!" for instance? Or are you just referring to the use of "vamos" instead of "vayamos"? I remember something about people hardly ever using the correct form of the imperative for this verb in Spain... Some of these mistakes natives make without even knowing it is actually grammatically incorrect :-)
Oliwia75, when I wrote that comment I was just thinking of vamos/vayamos.. but I just read in a book (La Ciudad de los Césares by Manuel Rojas) the sentence "ahora organicémonos bien", and I think that's imperative..
So, AdrianaLus, maybe it depends on the country and the verb and the context?!
Rob2042 made a good point: there's no question mark, so it is a "declaratory statement" (i.e., a sentence rather than a question).
As an aside, I used to watch a TV "game show", regularly, that came out of Mexico. The host of the game show was a lively guy named "Marco". After he stopped to joke with the contestants, for a minute or two, he would return to the game play by saying, "Vamos a jugar!", which--by interpretation--meant "Let's play!"
(He even used the phrase "A jugar!" to mean the same thing: but, the producers always seemed to be coaching him to say "Vamos a jugar", instead, as the shortened form was more of a regional [or slang] expression that the TV executive directors thought was below the quality of a top-rated television show.)
When I was much, much younger, I often heard "A jugar" (viz., "Let's play!"), in the same way that "A ver" means "Let's see!".
Mexico has some interesting traditional ways of saying things. In the old movies (with Mexican actors riding horses), the outlaws would hop on their horses, quickly, and say, "Vamos!" (Let's go!).
At other times, I heard the word "vámonos", on occasion. But, maybe this word is now out of vogue. (I'm not sure, though, as I have not visited Mexico in a long while.) And, things do change.
Here is another comment (please see my other comment, too).
I have been trying to ask Duolingo, on occasion, to accept that this type of phrasing can be conjugated into the future tense, in English, without any loss of meaning.
"Vamos a permitir esto." = We will permit (allow) this.
But, as with many things, the context in which something appears is just as important as the literal words, themselves.
"Pronto vamos a comer." = We are going to eat, soon. (Or, "we will eat, soon.")
But, just as with "vamos a jugar" (in the example I gave in my other posted response, here), the context in which this phrase was spoken, by a Mexican game-show host, seems to dictate what its meaning is, for us as English speakers. "Vamos a jugar" = Let's play! (in that context).
"Pronto vamos a jugar" = We are going to play, soon. (Soon, we will play.)
"Vamos a jugar pronto" = We are going to play, soon. (Let's play, soon.)
NOTE: There are many Duolingo examples of "vamos a....[+ inf. verb]". And, again, depending on the context, this form can be translated into the future tense, in English, or (alternately) as an imperative, right along with the typical "We are going to...[eat, sleep, play, sing, etc.]."
Naturally, the Duolingo examples don't give any kind of context, so one just has to "wing it"; but, my suggestion, here, would be this: when in doubt, just translate it literally, when a sentence begins with "Vamos a..." (or, even "voy a....", as well as applying to any of the other present-tense conjugations of the verb "ir").