Sri Lankan here. I'm not sure why you have the impression that asking a random person on the street for directions will result in your being scammed. That's certainly not the culture here. In fact, the many foreign friends I've hosted over the years tell me that your average Sri Lankan will go out of their way to help a foreigner—no fees, compensation, or other inducements needed.

You do want be wary of anyone who starts a conversation with you (as opposed to your starting the conversation with them). And yes, if you're in a "touristy" area, you do have a significantly higher chance of meeting someone aiming to rip you off. But these are true of essentially every country in the world—not just Sri Lanka.