Right on the money with Alan's response. I would bump the sign call up to 18%.
There are many, many communities that do not permit "For Sale" signs plus condos and many town home and villa communities.
This should not present a real problem.
The seller, however, should relize, selling the home WILL not be a community secret.
I would predict only 7.3 seconds after appearing in the MLS everyone in the community will know.
Condition for this eventualllity and go sell this house.
I have found, and you will also, that your greatest concern will be the appr 30% of sales originating from resident referrals. There is a cost involved. Overlay these restrictions with the projected number of showings and how that influcences the DOM and you will very likely get consessions via price or eventual permission to place the sign since everyone will evenually know. The absence of the sign only punishes the owner.
That is why you a real estate PRO....you have more than one tool in the shed. Work with what you have, overdue to communications with the owner (when no one shows up you will be blamed if there is a void in communications).
You will need to quickly assess if the owner is parnoid or if the neighbors are 'not so nice." If the latter is true, you MIST prepare for the sidewalk intercept and employ proper measures ensuring the 'not so nice' neighbor sidewalk intercept NEVER takes place with a potential buyer. These folks can prove to be very zealous in their venomous intent.
Best of success,
Annette Lawrence, Broker/Associate
Remax Realtec Group
Palm Harbor, FL