Taking the train is 55-90 minutes (depending on time/train) from Mahwah station to NY Penn Station. From there, you'd have to figure out your route and add time from Penn Station to your destination.
Driving in can be anywhere from 1-3 hours depending on traffic. On weekends, it can be as little as 45 minutes.
Never took the bus from up here, but I usually park at the North Bergen Park and Ride and take the bus from there.
Source: I do it!