Yes, there are rattlesnakes in the Sanctuary. We had our home built in 2003 but have since downsized and moved. There was a program for residents to learn about the timber rattlesnake. Some of the snakes had tracking devices on them and moved some distance; one to a camp in Medford. Although I never saw one on my property (John James Audubon Way), I know my friends on Benjamin West did see them there. I think as you get closer to the lake, you have more of a chance to come across one. If you notice, there are culverts under the sand road by the lake. That's where the rattlesnakes are supposed to cross through in order to avoid the road.
The snake issue is not a secret to anyone living in the Sanctuary. I do not think that the realtors developing there should indicate that there are no snakes; that's simply not true.
My advice would be to talk to the people who have been there when the first homes were erected on the newer development (John James Audubon side).