You definately need to get around with some form of transport (taxi or metro)unless you are bang in the centre and aren’t looking to go too far, but Barcelona is not nearly as big as London and definately isn’t as expensive. A taxi to the bottom of the La Rambla (Columbus statue) from Hesperia is about 7 Euro (Estimate) so between a few of you it is not much at all especially when the drink at the party is free!!!!!!!
In London this January I am keen to hire some of the old style double decker buses and get them sponsored with the persons brand on and use tehm to take people to hotels, parties etc. We definately wouldn’t be missed with a fleet of those!