JOURNEY AIPORT-to-BARCELONA and vice versa
I'd like to point out that the airport at Barcelona -there's only one btw!-, which is in the neighbouring town of El Prat de Llobregat, has these travel options to/from Barcelona:
1.) Taxi: there is a permanent taxi rank of at least 1200 taxis at the airport. A journey to the city centre should cost around 35-40€ which includes the compulsory supplements when applicable (http://bit.ly/BCNtaxi2016) Note that there are different fares depending on the time of the day and the day of the week, and the more expensive can be up to 40% more than the cheap one. In general, there are no gridlocks in the city, albeit traffic is very dense on rush hours (7:30-9:30am and 6-8pm). All taxis in the city of Barcelona are painted black and yellow.
2.) Aerobus: a private bus service from the airport to Plaça Catalunya in downtown Barcelona with 4 or 5 stops in the middle, one being Plaça Espanya and the rest along Gran Via de Les Corts Catalanes avenue. Cost is 5.90€ p.p. It runs 365d/year, every 5'/10' from 5am to pass midnight and the journey lasts 40'. http://www.aerobusbcn.com/
3.) Bus #46: a public line running from the terminals at the airport (T1 and T2) to Plaça Espanya, west of the city and a hub of the transportation network -many bus, train and metro lines converge there. It runs from 5am to midnight and the frequency ranges from 12 to 20'. As part of the integrated transport system of the city, the T-10 travelcard can be used here. Note on board only single tickets can be bought. Check tab "Bus" and tick line #46 to see the line on a map in the link above. At night, Bus #N16 from T2 and Bus #N17 from T1 serve this line, albeit they have different itineraries. The T-10 can be used also in these lines.
4.) Train R2 Sud: departing from T2 it connects with Sants, Passeig de Gràcia and Estació de França stations. Schedules here. Note the airport station is spelled "Aeroport" (Catalan). Journey takes 35-45' and frequency is every 30'. The T-10 can be used here.
5.) Metro L9: a new connection offer (read more here). However note it does NOT take you straight to the city centre as this line serves the northern part of the city. You need to transfer in order to get to the city centre. I advise against this line for newbies to the city as transfers are not so straight forward. Also note that T-10 is NOT valid for this line. Ticket cost 4.5€
I'd like to add that public transportation in Barcelona is totally safe, clean, cheap and efficient.
Enjoy!