While in Mazatlan, I rely on the bus system - I believe it to be the most economical and reliable transportation option in the city. I'm comfortable that I can get from the Cerritos area to the Golden Zone and El Centro, but other areas of the city "not so much".
Today I discovered an Internet bus route page (it appears to be a "work in progress") which significantly expanded my options for getting home from El Centro and for traveling to other areas in town.
It appears (from the list of bus schedules) that the finished product will be extremely comprehensive - eventually something very useful for Gringos and others in Mazatlan.
For years, I've been using the bus route map (on the left) that you find printed and distributed all over town. While it is still somewhat useful, you'll find that some routes have changed and some other added.
And finally, I found this "Bus Route Locator Map". If you can decipher it and find it useful, please post your secret in the comment section below.