My son is 5.8 and I still don't let him play alone even in our own fenced-in backyard. So would not let him play outside by himself either. Living in a housing complex would probably make me even more worried than living in a suburbian subdivision. I let my kids explore as much as possible, we even unschool so they get a lot of freedoms but this is not one of them. Being gifties seems to make them be even more at risk (in general). Their curiosity trumps their sense of caution. Probably won't let them be out alone until I feel they are ready to be home alone too. Right now I might leave them home alone for the one minute it takes me to go get mail from the mailbox but that's about it.
Not letting them play alone in your own fenced back yard seems a bit limiting. I let mine play in our garden by themselves (7.0 and 4.11). I let the older scooter round the block to a friends while we drive sometimes but usually we walk with him (the road crossing is first so I do that with him first). I have let them play at the park across the road while I got tea on provided they stayed in the area i can see from the kitchen. I let them climb trees and ride bikes fast down hills etc but the must wear helmets every one they go on anything with wheels.
Having said that ds7 probably won't be allowed to walk to school until he attends the intermediate across the road from our house whereas ds4 could probably do it now.
