From the airport you can chose between many ways of access to the hotel:
Aerobús: They are situated outside every terminal, it departs every 15 mins. and takes about 30 min. to get to the city center. It makes the following stops: Plaça de Espanya, Gran Vía, Plaça Universitat, Plaça Catalunya y Passeig de Gracia. The last bus of return leaves at 11.15pm.
Tren: The trains leave every 30 mins. The last trip is at 10.30pm, it takes about 30 mins. to get to the center of the city. You can get off in Sants (Barcelona's principal train station) or in Plaza Cataluña, which is much more centric.
Taxi: The taxi is a measured service, you can take it outside the terminal, and it will take you to the center of the city in about 20min.
The metro station is Parallel (L3 green line or L2 pink line). Its two minutes to the Hotel and both lines goes to the Barcelona important places.