you do not have to ask for permission if you are a GPAA member
carry your membership cards with you ( no one has every asked me to see mine) but you already have permission as a member.
remember most of the claims are BLM land or Forestry land. Public Access is granted TO EVERYONE. your membership gives you exclusive rights to dig for and extract GOLD. others who may be using the land to camp, fish, hunt, ect..... can all do that but anyone without a membership would not be able to dig or extract GOLD unless you took them as your guest or asked them to be your guest for the day.
GET OUT THERE AND DIG WITHTOUT WORRY- have a great time - hope this information helps you enjoy the claims!
your friend and fellow prospector