Green City soccer pitch is managed by Dulwich college and can be found close to Jinqiao Carrefour (that's what I yell to the cab driver when rushing off to play).

The entrance of the pitch is at Lan'an Lu, so you could also tell the cab driver 'Biyun Lu - Lan'an Lu'.

There's no real golden rule on how to get there.
You need to get to Pudong first (for those of us who live in the city).
The Yangpu bridge is closest to Green City, but then again, it's a bit out of the way from downtown.
(it is however a route with little chance on traffic jams... so if everything seems jammed up...)
Otherwise you'd make your choice of bridge or tunnel (consult your taxi driver for jam-free options) and head up Yanggao rd north and turn south on Yunshan road. Turn immediately left on Lantian road, pass the Decathlon store and parking lot and turn right on Lan'an road. About 100m further you'll find the entrance to the pitch.

Below you will find a scrollable map for more directions.
The pitch is indicated with 'zuqiu park' (soccer park), but it's actually rather the gray area just south of the green patch there...

You can also print out one of these files:
SPL_PITCHES_TAXIPRINTOUT_GREENCITY.PDF (a pdf that has all info, map and Chinese directions)
SPL_PITCHES_TAXIPRINTOUT_ALLPITCHES.PDF (a pdf only Chinese directions, but for all pitches)