You would be closer to hunts in Ringoes and in East and West Amwell from Princeton. Good hunts from stories I have been told.
East Amwell Hunt is about 20 min from Princeton.
Mercer Co has some good barns but is relatively more suburban. Hunterton County to the west and Monmouth, and Ocean to the east have more horse action. Mercer Co does have their own Equestrian Center tho. It is located on 260 dedicated acres adjacent to almost 3000 acres for riding.
Hey! my house is for sale, just down the street from Princeton!!