Travelgay.com and Patroc.com have good reviews on gay nightlife in BCN. I personally like Bacon bear bar, Night Barcelona for bars and The Black Room for music.
I'm also visiting in December just before Christmas.
I have only visited 1 sauna in Medellin(Club 55), and it was fun and felt very safe, but would be interested in a broader view - as am there for all of July