Bus might be an option ?
http://www.busplana.com/new2013/en/transfers/
Wow where can you find a car for that price? be careful you might have to pay for a full tank and perhaps other extras massive excess charges if you do have a knock, a credit card deposit will be taken! do use Gold car what...
It's very easy, the site below is in English, the ticket office in Barcelona Sants speaks English, so you'll be fine
http://www.renfe.com/EN/viajeros/
Salou Por favor billetes de ida y vuelta write dates down