Jmac,
We take the same flight (6pm Taca non-stop to JFK--5 hours, I love it).
I know they could keep my luggage for me, but I feel like a nomad going around town without a place to stay.
You can always shower at Zona Blue, that's what I did in October. Obviously, I mean after a session, I didn't just go in and ask Eddie if I can use the shower.

SL was keeping my bags and I hit ZB for a while and showered there. Worst comes to worst, that's always an option. (But I don't think they have shampoo in the showers.

)