We found a really good Morelia walking tour map and guide on the Vagabond Buddha website here. There is a link to a Google Map and the page has concise details about each stop on the tour.
The tour starts in the main plaza, but we decided to take it in reverse order starting at the "Alley of Romance" (Callejón del Romance). The Uber driver suggested dropping us off at this walking street a few blocks from the Alley of Romance at "Plaza Morelos" because there were more alters along the walking street and it is a beautiful area as well.