Are por qué no/ mejor no only used with vamos? Or are these phrases more commonly used for all commands (not just ir)?
For the road signs, are they third person singular for affirmative commands, and third person plural for negative commands? Or are both singular and plural third person used equally for either negative or affirmative commands?
Hola Devin P.
Great questions! Let’s take a look at each one:
First, regarding the expressions “¿Por qué no...?” and “¿Mejor no...?” — these are not limited to "vamos" or the verb ir. While “¿Por qué no vamos?” (Why don’t we go?) is a very common example, both expressions can be used with a wide range of verbs. For example, you might hear “¿Por qué no lo intentas?” (Why don’t you try it?) or “¿Mejor no salimos ahora?” (How about we don’t go out now?). These phrases are often used to make polite suggestions or invitations, and they typically use the indicative mood, not the imperative. So, to answer your question: no, they’re not exclusive to ir, though vamos is a very frequent and natural fit because it expresses joint action.
Now, about road signs and command forms: in Spanish, public notices and road signs usually adopt the third person singular (usted) imperative form, especially in formal or instructional contexts. For example, signs like “No fumar” (Do not smoke) or “Pare” / “Alto” (Stop) are aimed at the general public, using the singular formal command. Sometimes, signs also use the infinitive (like “Prohibido girar a la izquierda”) to express prohibition more impersonally.
Plural forms (ustedes) are generally not used unless the sign is addressing a group explicitly, which is uncommon. Both affirmative and negative commands on signs tend to keep to the singular formal tone, making the communication clear and neutral.
I hope you find this explanation useful.
Hasta pronto
Silvia
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