J Lo and A-Rod caused quite the scene Friday night in Queens ... with fans going insane.

They were strolling around Hunters Point Park and, let's just say few have hit the grass looking this good.

Earlier in the evening Jennifer performed at at 4th of July Concert in NYC. Alex was front and center and gave her a big fat kiss as she left the stage.

By the way ... JLo did not disappoint, putting on a proud display of what her mamma gave her.