Spanish language Q&A Forum

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?

This was a question on one of the quizzes:

Which of the following articles could you use with the letter "t" in Spanish: "te"? Then it listed “la, el, una, un” as options to choose from. 

I was unsure if it was referring to a word that started with the letter t, or the drink té, or the indirect object te. 

Kinda confusing.

I would translate this as "Take any dish."

Coge cualquier plato. 

I would translate this exactly the same way.

Under what circumstances would one choose to use either one?

Are these words indeterminate and/or invariable and what are the meanings or other examples of indeterminate and invariable?

If I wrote:

¿Puede venir cualquiera a mi fiesta? 

Can anyone come to my party?  Would that be incorrect?