The hall doesn’t have a postbox, or postal address as such, but its address could be described as:
Neuadd GoffaMynydd Llandygai
BANGOR
LL57 4LQ
Below is a Google Maps aerial photo showing the location of the village hall. There is a small car park opposite and cars can be parked along the road.
View Neuadd Goffa location in a larger map
Here is a Bing map showing Mynydd Llandegai.