Couple of points.
0) If you leave City Island at HIGH TIDE at the Battery
(consult Eldridge as someone suggested), you will have a nice ride down the East River and out the Narrows, heading for Sandy Hook/Atlantic Highlands.
Hellgate will not be an issue. Actually, the cut between Roosevelt island and Manhattan just south of Hellgate is the most challenging part of the trip with tug/barges, DEP boats, party boats and powerboats that don't know that throttling down is considered good seamanship. The riprap and seawall on each side magnify the waves from the wakes. We once took a complete standing wall of water
over the entire length of a C&C
35 in there. Beware and transit that portion quickly (which you will - it's the fastest current
on the East River).
In anything but a severe blow, there is good anchoring
(and relatively protected), at the east end of Atlantic Highlands Municipal Harbor. Your only other anchoring
bet is Horseshoe Cove, on the Hook itself, but that is not well protected in westerly winds. It will take you 1 hour in, and 1 hour out of Sandy Hook Bay, if you stay in Atlantic Highlands.
1) Watch out for commercial fishing
boats heading off the coast of NJ. They don't like detouring around anyone.
2) The advice
on Cape May is good and if your mast
is lower than the 55' clearance - the Cape May Canal
will save you LOTS of time. You can also take on diesel
in Cape May.
3) Timing - we did Atlantic City to Sandy Hook in about 12 hours motoring a C&C
41. To make AC or Cape May, some of your sailing will likely be after dark. You should consider the inlets north of Atlantic City only for a weather bail-out. Keep going if you can.
4) The approaches to Atlantic City are pretty shallow, pretty far out. Study the charts
and adjust your waypoints accordingly.