I happen to live nearby and use this trail for cardio on average two times a week.
To start, this trail is much longer than 2.3 miles. If combined with Fort Wadsworth GNRA it is about 4.3 miles. I highly recommend adding the fort as it offers unforgettable views of the Verrazano Bridge as well and Brooklyn and Manhattan skyline. It also adds few steep hills to climb. Although you would ride on the street through the fort, the car traffic is nonexistent. There is ample parking near the highest point on the property making it a good starting and ending point. During summer months, don't be surprised to see a herd of goats cleaning up the vegetation on the hills of the old fortifications :). If not exploring roads throughout the fort, you start downhill and keep as close to the shore as you can. You will pass the newly opened campground and continue on until you see a narrow passage going left (clearly marked). This is your connection to the NYC Parks. From there, the bike route goes along the boardwalk (paved) but you can ride on the boardwalk as well. You will pass numerous playgrounds, fountains, two restaurants (fast food and more upscale), playing fields and wooded areas until you reach the end of the boardwalk (with a nice fishing pier). From there you will continue along the beach (on pavers) until you reach Miller Field. There are water fountains and restrooms all along the way. As of this writing (7-2012) there is construction going on at the end of boardwalk so if you are riding along side of it, you need to get on to continue. There is also a pathway extension project to extend it past the Miller Field. It will add about 1/2 mile in a nice beach front yet wooded, shaded area.
This bike trail is great but you have to be careful. There are tons of joggers, rollerbladers, kids and beach goers so keep you speed under control. Hope you come to visit, I’m sure you will enjoy it.