As a non-technical founder, would you use an agency to build your MVP?

There are a lot of "it depends" (the product, the agency, the deal etc.) but since you asked a simple question. I'll just say "yes". If hiring an agency is a way forward and the opportunity is to stop/not start doing business then yes do hire. I think it helps to make progress and potentially attract technical co-founders see https://news.ycombinator.com/item?id=39902372

Yes, as with an agency you get a team. For example, we build MVPs and we offer consultancy, design, development, deployment. And the resources we offer is full time.