I already recommended that if possible use the train to get to Rehovot. Anyhow, this is the central bus station, you can take a bus from here Tel-Aviv, Jerusalem and many other places. You can also use local city buses if you need to go to the suburbs of Rehovot.
Usually you will come to this place by car or bus, but actually the train is the nicest and easiest way to get here from Tel-Aviv and by this avoiding all the traffic, especially during the rush hours
I wrote already about the train here, but I just wanted to add this example picture from the train station. Just a reminder of the 3 languages used in Israel.