Surgical masks were really designed to protect the patient from the surgeon, not the surgeon from the patient. They will be much more effective in preventing you from spreading the disease you have, rather than protecting you from getting the disease you don't want to get. A mask may have some effect in protecting you from getting a virus. A very minimal effect. Just like wrapping your head in toilet paper (if you could find any) will have some effect...

I am guessing here, and have no scientific evidence, but I would propose that staying 6 feet away from an infected person without a mask might do you better than being 3 feet away with a mask. I'm talking surgical type masks here. Not the positive pressure, air tank fed, sealed facemasks like firefighters use.