Wirelessly posted (BlackBerry8703e/4.1.0 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/104)

If I were making the OP's trip, I would probably walk or cab over to 50th Street and 8th Avenue, and catch a Queens-bound E train for the 20-minute ride to Roosevelt Avenue/Jackson Heights. From there, either a taxi or the Q33 bus to the US Air terminal. But a taxi from 11th Avenue would almost certainly get you to LGA by 8:15-8:30, even after considering the theater traffic likely to be found on the West Side in the early evening.

(You would probablt get more responses to this question if the Mod moved it to the NYC forum.)