Throughout the episode the character acts very flamboyant but is apparently straight. When Homer sees Marge's silhouette through the cabin window, Marge tells Alberto to hide in a chest at the end of the bed.
Homer drags the chest outside and when he sees Sylvia he stuffs her in the chest as well, resulting in Alberto and Sylvia meeting. Five years on and it's the present day.
Homer, Marge and the kids have arrived at Kozy Kabins once again and they see Alberto, Sylvia and Ruthie. They thank Homer and Marge for not seducing them otherwise they would never have met. Alberto is European.