If you prefer not to use the local transport of Barcelona, or drive yourself then the taxi is a very good option.
The taxi in Barcelona is very cheap, compared with, say London where I always found the taxi fares expensive. From my expereience, they are not into "ripping off" the tourists and are usually quite friendly and will offer you amicable conversation, even when you do not have a clue what they are talking about (unless you are of course fluent in catalan!)
Another great advantage of taking a taxi in Barcelona is that they are easy to come by and you will not be standing waiting on some street corner for hours.
It does, however, become a little more expensive for transfers to the airport but for travelling around Barcelona city it is cheap and quick!
