Google search, first itEM, uncovers: "5) Little known secret that I'm sure I'll kick myself for sharing later: If you live in Washington Heights, you can catch the Fairway shuttle 4 times a week (T@5:30, R@6:30, Sa@10 and 11) in front of 80 Haven Ave (170th street and Haven). The van comes promptly, gets you there in 10 minutes and you have 50 minutes to pick out all your grocery items and pay and it leaves 1 hour later from the parking lot. (except the 10 am shuttle on Saturday--that gives you an extra 15 minutes). The Fairway shuttle is perhaps one of the top 10 things that has changed my life in New York. Just look for the gaggle of people clutching their Trader Joe's reusable bags and follow them onto the van."
Fairway shuttles can be arranged for groups of ten or more. Check if any large co-ops or university-type places have a regular stop. Maybe you could call Fairway and see if there are stops in your area. Our co-op near 125th St has two runs a week and I know one of the Teachers College housing units does, too.