Teaching Stranger Danger?

DS has PDD-NOS and is VERY friendly and social...to a fault. I also think due to having so many therapists and teachers, he is very adult dependant and seeks them out for playmates. This is becoming a problem when we go out somewhere. He will literally go up to strangers, grab their hands and ask them to play with him. I saw ont he parenting thread about "tricky people" but I do not think he'll get the concept (he is about to turn 4), especially since HE is the one seeking THEM out! I also do not want to scare him either. I tried to start a conversation about how not all adults are nice and you need to be careful, but it was clearly not enough. I do not want to make him fearful of adults but I do not know how to get it through his head that he can't be in the park and go off with a stranger

Teaching Stranger Danger?

DD is also very friendly and stranger danger took a while for her to understand. We did lot of social stories and the school worked with her quite a bit. DD is also very literal. There is no grey area with her so she now is extremely aware of stranger danger to almost a fault. We taught her she is not allowed to talk to any adults without asking mommy or daddy or her teacher first. We also included some community people with that such as a firefighter or a police officer. Now she will not answer anyone without checking with us first. She is not fearful of them, she just understands that is the rule. Even on vacation if someone talks to her she turns to us and asks if it is ok or she just ignores then. Alot of people think she's rude but I'd rather her be rude then to go off with someone dangerous. But long answer short...social stories did a great job along with repetition.