It is downtown roadway, but it is very driveable pulling an RV. The only part that would be hard is the turn onto Marin, but you are almost to the river, so the traffic is not really heavy any time of the day.
The PATH train (Cost is $2.50 each way) to either Times Square or the World Trade Center is located about 3 blocks away. It is a good 7-10 minute walk, but is safe and through a nice clean neighborhood. We took our 2 children, aged 8 and 5, back and forth and a couple of times, after midnight and never felt unsafe.
There is a Light Rail station just outside the campground/marina, but we never used it, but walked another block and a half to the PATH. We did a little $$ figuring and it was going to cost us about double to use the light rail.
Although I do not like NYC, my family does and Liberty Harbor is a good place to stay, convenient, clean, great view and close to restaurants. It is NOT cheap, but it is all of the above.