Hi can I suggest that you try the following websites, I have used both many times and have no complaints. www.alpharooms.com & roomsnet.com. Hope you enjoy your trip and as I am taking a cruise on the same ship in June would love to read your review on your return.
I can recommend the Citadines Ramblas Apartment Hotel located in the Ramblas area. Reasonably priced, convenient for everything in the city and only a 5/10 minute taxi ride from the cruise port.