For someone who says exactly what they think

No tener pelos en la lengua

no teh-NER PEH-los en lah LEN-gwah — To not mince words

"Mi abuela no tiene pelos en la lengua."
My grandmother doesn't mince words.

Literally "to not have hairs on your tongue" — said (usually approvingly) about someone who's bluntly honest.

"This describes my grandmother perfectly, and honestly most of the women in my family."— Graciela