Hi Sam
the Abrat is a great location, literally five minutes walk from some great sun set bars which should still be open at the end of October, Make a note of bars like coastline, kanya and kasba which are just a couple of minutes walk from you7r hotel. And bars like Mambo, savanha, cafe del mar another five mintues walk, I am staying in the same region in July this year love that part of san antonio more than any other.
You will find that the notorious west end area will mostly likely be closed although you might find a few bars open. As for english, the majority of tourist on the island, well san antonio in particular are english and you will find like minded people around your age and older in the sun set bars as these are a little more up market and cosmopolitan.
Have a look at this link, its a forum i use to get my ibiza info, try searching for the abrat hotel or sunset bars on it and you will get loads of info.
http://www.ibiza-forums.com/
cheers