Shanghai Rugby Football Club is found in Waigaoqiao.
It is only 100 meter or so from the 'line 6 wuzhou road' metro station (on the east side of Zhangyang north road), so that's your safest bet.

You can of course take the subway there, but if you have a preference for risking your life and would opt for a taxi ride, best tell the driver 'liu hao xian wuzhoudadao ditie zhan, waigaoqiao'. And if he doesn't get that, you could try 'Zhangyang bei lu kaojin wuzhou dadao, waigaoqiao' (the field is 100m north of the Zhangyang north road # Wuzhou Avenue crossing).

Below you will find a scrollable map for more directions.
The pitch is not on there, but Zhoulan Road metro station is.
And if you can't find the field from there, well then there is no help really.

You can also print out one of these files:
SPL_PITCHES_TAXIPRINTOUT_SRFC.PDF (a pdf which shows most of this info and also Chinese)
SPL_PITCHES_TAXIPRINTOUT_ALLPITCHES.PDF (a pdf which has Chinese directions for all pitches)