Mazatlan is a great, safe place. But it is not the garden of eden.
This afternoon, around 1 p.m., a couple who live here and are not novices, were walking on the Malecon, north of the cliff divers and just south of Los Pinos, when a couple guys on a motor cycle snatched the lady's very thin gold necklace. One guy was parked with the bike on a corner, the other snuck up behind them, grabbed the necklace, and ran to the motorcycle and they were gone.
This is a very difficult type of crime to prevent, but use situational awareness. If you see two guys on a motorcycle, eyeball them. Don't confront them. Just make eye contact. Let them know you see them. If they seem to be looking at you, if the make a U turn, if they drive around the block, STOP. Again, you don't have to confront them. Just stop, put your back against a building (Or the sea wall if on the Malecon) and face them. They rely on surprise. If they cannot sneak up behind you, their plan is down the drain. Cross the street. Walk up to other people. Go in a store. Just break up their plan. They are not into hard work to rob you. They are lazy and cowards. Anything you can do will foil their plan. But you must make yourself aware.