I have a layover on a Sunday from 9:00 am to about 5:30 pm (the first leg is a domestic flight with AA arriving at LGA, the second leg is an international flight with Finnair departing from JFK). So I'll have an 8-hour window. I'm thinking about spending a couple of hours in Manhattan, just walking around (I think I'll only have a backpack). What is the best way in terms of transportation? (I don't consider Uber since it'll be too expensive.)
Let's say I want to go to the area near the Carnegie Hall and I don't want to spend more than $20-25 each way. (But even if I land at a different area of Manhattan, I think I can walk to another its part - as noted below, I'll have 4 hours.) At some point, I considered a shuttle, but the one I found starts operating at noon or something (on Sundays).