There has been an usually high number of deer sightings in our area lately. Deer are common in this area, and are likely being noticed more because the Spring is birthing season.
You may observe a young deer 'left behind' in your yard, or a group 'not leaving the yard'. This is normal behavior for moms to leave their young while searching for food, and groups usually stick around certain yards for either food and/or safety until they move onto the next property. It is unlikely that deer will remain on one's property for longer than a day or so if there is no food/safety source.
If you feel it is necessary to deter them from your property, it is recommended that homeowners visit a Lawn & Garden or Outdoor (sports) store that may sell actual deterrent products. It is always recommended that residents make sure there is no food source accessible, such as a garden or open garbage (which applies to other wildlife animals as well).
If the concerns are more population related, please contact NJ Fish & Wildlife. Attached is info from the NJ Fish & Wildlife website.