We spent over a month in Mazatlan, second largest city in Siniloa - the largest being Culiacan about 90 mins drive north. When we'd take the bus into town, we'd pass the condo building where El Chapo was arrested the first time.
We've spent the better part of the last 4 years in Mexico, mostly Ensenada just south of Tijuana. Ensenada is listed as a very dangerous city. It was not our experience at all. We felt very comfortable in Ensenada, though we have traveled a lot and take normal precautions and we don't have bad habits that would put us in harms way (we go to bed early, don't drink too much, don't do drugs, etc.).
While I find Mexico exceedingly safe and comfortable, I have to say that life is short and if you're worried about this type of stuff, don't come to Mexico. Your free time is too valuable and peace of mind, even if founded in myth, is worth too much to white-knuckle a trip anywhere.
It's sad that Mexico has such a bad reputation in the US. Americans love Mexican food, love to visit the all inclusive resorts, enjoy low restaurant rices due to cheap Mexican labor, but we generally look down at Mexico. I could go on for pages what a mistake that is but in the end, if that's the perception, not much I can do except to say I love it here. Mexico is incredibly family oriented in a way that the US hasn't been since the 1950s. I find the people warm, friendly, and helpful.
Good luck with whatever you decide
Peter
PS - turns out gangsters don't like living in crime ridden areas either. Little Italy in NYC was known as an incredibly safe neighborhood when the Mafia ruled. Guessing Siniloa is too.