Los cuernos están en tu mente

[startrek2001]

que quiere decir," les cuernos están en tu mente"

[Rusty]

That should probably be "los cuernos están en tu mente."
Without more context, a proper translation can't be given. There may be an idiomatic use or a play on words we don't know about.
The literal translation is "the horns are in your mind."

[pjt33]

Without further context, I'd assume that this is part of a fight between a couple. One of them accuses the other of having an affair, and this is the denial. "Ponerle a alguien los cuernos" is to cuckold them.

[Perikles]

Originally Posted by pjt33

Without further context, I'd assume that this is part of a fight between a couple. One of them accuses the other of having an affair, and this is the denial. "Ponerle a alguien los cuernos" is to cuckold them.

I thought that only men could be cuckold. Can it also apply to women these days?

[AngelicaDeAlquezar]

The context would definitely help, but I agree with Pjt that it looks like a fight where someone thinks their partner is cheating on him/her.

Los cuernos están en tu mente -> Te imaginas que te pongo los cuernos (pero no) -> I'm only cheating on you in your imagination.

[pjt33]

Originally Posted by Perikles

I thought that only men could be cuckold. Can it also apply to women these days?

I couldn't think of a sufficiently elegant way to express it, but Angélica is spot on with "cheating".

[JPablo]

I agree with Angelica and Pjt33. Context would help, but the interpretation seems rather spot on.

[CrOtALiTo]

I agree with Angelica.

Already here in México the word Cuernos en tu mente o cabeza means the infidelity of both genders.

Sincerely yours.