There is the Atlantic Beach Hotel and Bar (gay hotel/bar/beach) in the Condado area on Vandig Street. It is about a 10-15 minute taxi ride from the pier. The bar overlooks the beach. If you are there on a Sunday they have a Sunday Tea starting around 5:00 pm. The bar opens up at 11:00 am to 1:00 am daily. Lots of locals and tourist that are staying at the hotel. (beware quite a few hustlers there also, even though they have tried to clean that up)
Finding a taxi back is easy walk up to Ashford ave. make a left and walk a block to the Marriot hotel ask the door man you need a cab back to the pier, cabs are abundant there. Just make sure you give him a nice tip.
The only place that gets going early is the Beach Bar at the Atlantic Beach Hotel. Everybody goes there in the afternoon and early night and then head to Eros later. It is located right on the beach in the Condado area and it is on One Vendig Street. Hope this helps you. Enjoy the cruise. I will be on the Golden Princess on May 23 out of San Juan.