Because we had the Nuvali sticker, the guard let us through and told us we could use the same way going back.
We followed the road and took the Gate 1 exit, which led us to the corner where Caltex is located (exiting Nuvali Central via the rotonda towards Silangan exit will bring you to this same place).
According to boyong, who left a comment on my previous post on Canlubang, another option is to exit via Gate 4, which will lead to Canlubang Main, Ceris 1, I-mall, Don Bosco, Mayapa. I asked the Nuvali guard about it, but he was wary to suggest that route unless I knew my way around the area/town. Will explore at another time, but many thanks to boyong just the same for the heads up!