I would say less than 5 miles based on the RunDisney half marathons. It is usually mile 9 at the Stadium and back to Disneyland by mile 12. And it is just down Katella Ave. We went to a game several years ago while visiting Disneyland and took the OCTA bus that runs on Katella. It was cheaper than a cab and before Uber but I wouldn't hesitate to ride the bus again since it is such a short ride and I think the bus ran pretty frequently and the stop was right in front of the stadium.