Ask HN: where to get customer opinion for early concept?

In the "Startup Owner's Manual", Steve Blank stresses plenty the need to get out of the building and get customer feedback about anything it is that you're doing.

In the case of my product (we're still in customer discovery phase), it's tentatively aimed at stay at environmentally friendly stay at home dads or moms. The problem is that being in the SV tech bubble, and only ever interacting with tech people and entrepreneurs, we're having a hard time getting an idea if that's a good product/market fit. We're in fact going close to nowhere.

I'm an engineer who's just now starting to figure out how to be a "hustler", and so I'm pretty fresh when it comes to getting random people's opinions. Where should I go? I'm thinking either online forums (again, probably my tech bias showing), or in person at stores (can't imagine this would have worked well for companies like IMVU and Stardoll, chasing 13yo girls down Toys R US aisles for customer validation) or some other meetings of our hypothetical core user. I think the guys from Food on the Table went to some kind of homeowner meetings and tried to pitch their idea there.

Any suggestions?