There are some stealth camping opportunities in the Delaware Water Gap National Recreation Area and in Worthington State Forest, which Old Mine Rd. passes through, but you had better hang your food . There are a good number of bears in the area. Worthington has a campground that is open year-round. It's $25/night for out of state residents. One fo the group sites has a bear locker.
South of there, you might be able to get away with camping along the D&R canal trail that runs along Rte. 29 south of Frenchtown. The trail is heavily used, however, so you might not want to pitch a tent until dark. Also, without full foliage growth that time of year, you will be visible from the trail. I don't think the rangers patrol the trail at night. No budget for that.
Dog Wood Haven campground is across the river from Milford, NJ. Don't know when their season starts, but the owner, Mark, is very nice. He has charged me $15 both times I have stayed there. South of New Hope, PA, stealth camping options ar every limited as most of the land is developed. I know some places on the Schuykill River Trail near Conshohocken.