I have Figured out how to allow 1 group or more to get through and invisible wall with worldguard here is how.

/region define [region]
/region flag [region] entry deny
/region addmember [region] g:[permission group] <-- note there is no space between the colon and group
/region flag [region] entry g- nonmembers

IMPORTANT: You must also add the permission node "group.[permission group]" to the group you want to add.

Now let me explain it using an Example.

Lets say I have a region named Stuff and a group named CoolPeople and I want to allow them access to this region. I would type...

/region define Stuff
/region flag Stuff entry deny
/region addmember Stuff g:CoolPeople

 Then I'd add the permission node "group.CoolPeople" to the CoolPeople group in your permissions plugin's config.

Hope this helps anyone who was confused with this particular flag!