Fortunately, even though the plantation is a commercial site, it's open to the general public - offering the opportunity to leave the city and suburbs for a short walk on the slopes of the Table Mountain mountain range. The forest has a picnic area (a little before the entrance to the plantation), but IMO it's far nicer to enjoy a snack at the plantation's tea room and then take a short walk into the woods.
For details about the MTB trail, visit mtbroutes.co.za - they have all the info you'll need to plan a fun MTB ride.