Traffic really depends on daily basis, accidents on NJ Turnpike etc., It is usually not that bad If you are slightly earlier than 7:00 am in the morning. Between 7:00 and 8:00 am, it is usually tough. Ideally, If you can find an alternate route so that you do not have to drive on Rt.18 much, would definitely save you time.
The best thing you can do is travel the roads that you will be taking at the time you will be on them for your commute. Try a few different days of the week and decide if the traffic is
"terrible" or "tolerable" for you.