I would say that Santa Marta is basically divided by two hills into three parts. If you're standing in Santa Marta and looking out into the sea, behind the hill on your left you get Rodadero, and behind the hill on your right, you get Taganga.
Rodadero is popular among national tourists, in fact in times of high season which is in December to January around Christmas time and in April for Easter, it is literally full of national tourists, so much that it gets hard to pass through it by car during these times. It is also a very popular residential area, where a standard apartment comes with a swimming pool in the building, parking space, security, sometimes a gym, sauna, playground for kids, and more. If you keep distance from the busy tourist city center, it is a nice place to stay long term. For example, Playa Salguero, a very popular calm area with a nice beach, Rodadero Sur or Rodadero Reservado. What I personally like about Rodadero Reservado is that it is close to the hills, where you can, in the early mornings before the heat hits in, take nice walks and you are in nature and yet so close to the city. That is for me something very unique which you don't find in many places. The walk leads you to almost virgin beaches of Inca Inca and Calderon. Almost virgin meaning that people can only get there by boat or by foot, by car it's (almost) impossible. The beach of Rodadero is broad and clean, but also very touristic, but I believe it's big enough for everyone, for everyone who doesn't mind crowds of people.
Taganga is a very popular backpacker destination with no paved streets, hippie energy, and full of dive centers. I would say it is what you want to see if you want to experience "typical Colombia". Maybe that’s why it is so popular among travelers. But where the tourists are, there is money, and where is money, there is a crime. Taganga had got a very bad reputation over the past decade, which might have discouraged many new tourists from visiting. But I can ensure you there is nothing to be afraid of as long as you don't "give papaya", a Colombian expression for provocating and pushing your luck too far. For example, walking drunk in a little dark street in the middle of the night with a phone in your hand or a camera around your neck, jewelry, an expensive watch, you get the point. People are actually very friendly, and will always greet you with a smile, as is known by Colombians. Most of the beach in Taganga is occupied by boats, most of the dive centers, together with our Sony Dive Center, depart from Taganga bay, but there is a space to swim and relax on the side of the bay. So if you want to experience more laid-back tranquil energy, Taganga is definitely a place for you.
If you decide to stay in Taganga we can recommend you a cozy room in Casa Tara.
Santa Marta is the city of opportunities, the opportunities to invest, to create, to make your dreams come true. As you walk through the historic city center, you can enjoy not only the beauty of the traditional architecture but also many little corners full of crafts, innovations, and delicatessen. At night Santa Marta transforms into a big party place, from where it got the famous phrase "Santa Marta is crazy." In Santa Marta you don't sit and stay drinking at one place, you drink and dance through many bars even if you're not a dancer or a drinker. The energy will just pull you in. So if you want to be close to the center of things, Santa Marta historic town is definitely a place for you to stay.
Los Cocos is a district of Santa Marta located right next to the sea, close to the Marina International of Santa Marta. It is similar to Rodadero, full of high-rise apartment buildings with almost each having its own swimming pool, The advantage it has over Rodadero is that it is a close, walkable distance from the historic city center and relatively safe (again without giving papaya). It has a calm beach, where the water might seem dirty at times of the rain, as it is close to the river which brings all the pollution from land. I swam there when I just moved in from Europe as I finally lived by the sea, I was not going to miss out on the opportunity of just walking out of the apartment 2 blocks down and taking a swim in the ocean.
And the last area which would be for me worth briefly mentioning is Pozos Colorados. It is an area on the way from Santa Marta to the airport. It is a little further away and one needs to accept the commute but it is very calm, mostly residential and with beautiful long beaches.
No matter where you decide to stay, it is worth it to have an easy-to-reach spot, on the balcony, rooftop, or on the beach, to watch the sunset, as the sunsets in Santa Marta are just unbelievable!