If you've got a car and you like short rides with low traffic by the river, you might also try:
* Nyack Beach State Park (in New York) -- north from Nyack NY, park near or along Broadway, or at the north end of Broadway, and (on a non-wet day) ride north along the river, then back the same way.
* Piermont NY: can ride east out to the end of the "pier" of Piermont -- though it's a bit tricky to find the non-private start of the road. Or can ride south from Piermont into Tallman State Park and explore (and there's other parking areas for Tallman).
P.S. parking in Fort Lee near the GWB for non-residents can be tricky, read the signs very carefully. If you don't see any sign restricting parking for non-residents, then look more carefully.
Also they have been known to lock the parking lot of Fort Lee Historic Park at night, and especially on a cloudy or rainy evening, the park administration's interpretation of "time of sunset" might be earlier than what you'd read on an astronomy or weather website.