We got the reality star/entrepreneur Wednesday at the Grove in L.A. for a book signing, and it's apparent from the crowd that braved really crappy weather -- people are into her and her story.

Paris says it feels incredible to have a son -- Phoenix Barron Hilton Reum -- and she was very open with our photog ... the kid's opened the floodgates for more babies.

It's interesting ... PH almost always holds her cards close to her vest, rarely opening up publicly about her intentions ... so it was a little surprising she played her hand.

Paris hubby Carter Reum announced they had a baby back in January after struggling to get pregnant ... and after tying the knot during a luxurious 2021 wedding weekend.

The "Simple Life" star can clearly keep a secret, even from her mom. No one knew she was having a baby until after the kid was born.