Jennifer Lopez took a trip to Central Park in NYC Friday night, to rehearse for the big concert Saturday.

J Lo hit the stage with Ja Rule and LL Cool J at around 8 PM and went through the paces, rehearsing 5 songs. They were on stage for a half hour, prepping for Saturday’s Global Citizens Festival.

Two of the songs were collabs with Ja Rule and LL … 3 were J Lo’s, including “Dinero.” She and Ja Rule sang “Ain’t it Funny.”

The woman who just said she feels like a Hollywood outsider will be at the center of the action tonight. And, it’s a good bet Ben will be watching … and cheering, and maybe even busting a move or 2!

Ben and Jen have been inseparable for months, and, as we reported, they are looking for houses together in L.A. — super-expensive houses, with price tags that go north of $80 million.