Ah, found it (err... repeated in most of the song, actually). OK, here's what I hear:
"Tonight we goin' be hittin' the floor." or "Tonight we goin' be hip on the floor." (Which sounds a bit tacky.)
"Be 'it' on the floor" makes little sense, but then again this is pop music. No, she doesn't sing 'proper' English, if you mean following a logical process, grammar or pronunciation.
Sorry to say, I remember the melody from many many years ago, and J-Lo's
remake doesn't do it justice (plus only giving us half the melody). :/ Just my opinion.