Starr, sounds like you have had some bad luck in Mazatlan.
Hope these tips get to you, but here are two sure bets:
* In the terminal, you can do a city tour thru Marlin Tours in an open trolley style bus for $15 ... takes you to all the viewpoints and sights. Great value.
* Randi's Happy Horses is great. My sister just did the tour and loved it. $45 per adult. www.randishappyhorses.com
You are probably too tight on time to book a private tour with Frank, but he's always great too for the Colonial Villages tour (which I took with him)
Try Mazatlan again ... I like it much more now.