Does anybody know details of alternative transportation from barcelona to costa del sol that would be quicker and/or cheaper than driving.

It's about 1,000 kilometres, so I would say that petorl is going to be between 10 and 15.000 Pts, depending on the car and how you drive. See if you can get a flight at the last minute?

The Euromed runs to Alicante in about 4 hours or so. This is a much cheaper option than driving.
http://www.renfe.es/empresa/glineas/glineas_euromed.html

There are also TrenHotels which follow a similar route at night more slowly. From Madrid, there is the Alaris which will get to Valencia in 3 hours.

I do believe that Alicante is on the Costa Blanca, however I can recommend the Euromed Barcelona to Alicante. We had a fantastic return trip I booked over the net using Tiknet on the RENFE site and we were so delighted with the prices (they even give a discount if you travel both ways) that we upgraded to Preferente. Wonderful
By the way Madridman, thanks for the compliment! I love being referred to as a junior when I am in fact a fully fledged member of the Silver Surfer Brigade