Check out this billboard on L.A.'s famous Sunset Strip -- it's got a simple yet powerful message: "DON'T F WITH JLO" ... and while some driving by might initially think it's J Lo herself sending a warning, the Netflix logo accompanying it makes it clear it's just a clever promo for her new flick.

The marketing team nailed it ... especially 'cause the film revolves around her character, Atlas Shepherd, a data analyst who has to rely on AI to save humanity -- so yeah, she'll be doing some serious butt-kicking when it hits the streamer Friday.

TBH ... ya might not want to mess with the real Jen, as a reporter at her "Atlas" panel discussion in Mexico City discovered upon asking her about any marital issues with Ben Affleck.

J Lo fired back with a damning, "You know better than that!" She was smiling, but clearly not pleased the question was asked at all.

No doubt about it, Jen and Ben's marriage is the talk of the town lately. As we first reported, the couple hit a rough patch and are now living in separate homes in L.A.

Since then, Ben's been spotted with his wedding ring off, then on again -- and then the duo played happy family with a dinner date ... before Jen showed up solo to her "Atlas" premiere.