Though not in Barcelona, I am in Spain and employment prospects for EFL teachers are good despite the recession. Doing the course in August is ideal because you'd be on the ground at the peak hiring time. Some schools even offer their graduates a job on successful completion of the course.
I actually did my CELTA in the Barcelona area a couple of years ago. I chose that particular provider because at the time it was the only one offering the five-week option. Don't get me wrong, the course was still incredibly intensive but that extra week gave me a little breathing space which undoubtedly had some bearing on my final grade, a Pass A.
Should you be interested in going with the same provider, you can find all the relevant information here: http://www.cambridgeschool.com/
(click on 'teacher training' in the top right-hand corner). Note that they are based in Granollers, which is about 40 mins by train away from Barcelona Sants station.Accommodation
The best sites (that I know of!) for finding accommodation are Idealista (http://www.idealista.com/en/
), Enalquiler (http://www.enalquiler.com/
) and Loquo (http://www.loquo.com/en_us
). Note that Loquo is a little like Gumtree in the UK and thus you may be able to buy a second-hand bike there too.Transport
For transport within the city have a look at TMB (http://www.tmb.cat/en/home
). For regional or long-distance trains you'll need RENFE (http://www.renfe.com/EN/viajeros/index.html
Hope that helps. If you have any other Qs, please ask and I'll do my best to help (although most of my knowledge is Madrid-related!).