Travelling on the metro could prove to be problematic if you are wheelchair bound, although work is being carried out to remedy this. Currently the only line that has a lift at all stops is the Purple Line, L2. On other lines, many stops still only have stair access and, although you could ask a member of staff for help, this is not ideal.
Travelling by bus could very well be the easier option because many buses have been fitted with disabled access, and recognising these is easy because they all have the international disabled access sign on the outside.
The third option, of course, is taxis. It will cost you about €5.00 for a ten minute taxi journey in Barcelona, which is enough to take you from one side of the city to the other. Licensed taxis are yellow and black with a green illuminated light on the roof to indicate whether they are available or not. If you would like to order a taxi that has been adapted for wheelchair use, try Taxi Amic S.L. Carrer Taulat 24, 08005 Barcelona. Tel: +34 93 420 8088.