You'll probably get lots of good info and suggestions, but I'll get the ball rolling.
Pueblo Bonito Emerald Bay is a beautiful resort, as upscale as it gets in Mazatlan, but it is miles away from anywhere interesting! This suits many people, who swear by it, and all-inclusive is really essential, although you do have regular shuttles to........
Pueblo Bonito Mazatlan, which is at the north end of the Golden Zone, excellent location for many restaurants etc. It is an older property, but well-maintained with first-class service. For most posters on here, we don't recommend all-inclusive, as the options outside the hotel are many, very good, and very reasonable in price....all-inclusive food can become a little, well you know, after a while! However many will take the all-inclusive and still go out as much as they wish, it all depends on the deal you can get, and the benefit of round-the-clock drinks is not to be sneered at....yes?
Both hotels are on the beach, the one at PB Maz is rather more user-friendly, and another advantage of this place is that the buses stop right outside the gate so you can get to the old city, which you must at least once, easily on the big green Sabalo-Centro bus, every fifteen minutes or so.
So much to do and enjoy in Mazatlan, friendly, helpful people all over, but for us, Emerald Bay is too far out.