I stayed 2 months in Freddy and Alejandro’s Airbnb.
To get to the apartment from the airport:
I took the train that's connected to the airport. I bought a T50/30 card directly at the train station. For 43,50€, the card buys you 50 trips to use in Barcelona within 30 days. It works for both train and metro, except the metro from the airport. Using 1 ticket I, I took the Rodalies train, got off at Passeig de gracia station then stayed on the same platform to wait for another train that brought me to Estacion de Francia. From there, I took a 4 minute taxi ride (3,30€). All taxis accepts credit cards,
Freddy and Alejandro are very responsive, friendly and helpful. They were there when I arrived to give me the keys and answer all my questions.
The apartment itself is a no fluff, rustic but functional space located on the first floor. It has a balcony, a washing machine, a double bed in a closed bedroom, a sofa bed that makes another double bed in the living room and a good wi-fi connection. A friend came to visit me. She slept on the sofa bed and the space was enough for 2 people.
The beach, the beautiful Passeig maritim and Barceloneta metro station are 5 minutes walking distance.
A medium sized supermarket called Spar is literally 10 steps away from the apartment (closed on sundays).
There are a lot of restaurant options (seafood, meat, vegan,) very close by. Baluard and Balboa are 2 good bakeries that are just a few steps away. (Balboa is opened on sundays).
Barceloneta is also next to (walking distance) El Born & Gotico neighbourhoods. They are a must see.
I easily was able to buy a sim card at Locutorio Interspace witch is a 7 minute walk from the apartment.
Barceloneta is a good choice if you want the beach and also be close to everything else. Just keep in mind it's a lively (and by lively I mean noisy and loud) and touristy place.
Spain is always a good idea. Disfruten