Thank you for the diagram as it is very helpful.
Will you be allowed to put equipment on the telephone pole? Does it have power?
What is your budget and reliability requirements? If you put something on the pole, you want to power it in such a way that you can do a hard reboot on it without climbing the pole.
54gl's aren't PoE capable, but there are some special adapters that can make it PoE easily.
Depending on the construction of the building (glass, wood, etc) I don't know that I would be comfortable with one AP providing coverage for both inside and outside the restaurant. I would at least like to see one inside and one outside.
I'm guessing that this is for customer access? Will you be using this same Internet connection for the PoS system and other internal devices?
Where in Northern VA? My family and I are driving to Baltimore from Arkansas later this week. If you are remotely close along the way there or back we could stop by.
P.S. Is the restaurant open? I'll do a lot for a good meal... :)