Hi g1ant - I won't go through listing restaurants or accommodation as although I live here (not in Bs As) there is already loads of good info to be found here posted by more knowledgeable people than me.

You won't need to worry too much about your lack of Spanish...if you can manage to get the basics right you'll be okay. October is a nice time to visit the city not too hot and not too cold. I would just say relax and enjoy the atmosphere of BA - a week is about right to see everything in a relaxed manner.
I would also recommend a couple of trips out of the city itself....a ferry over to Colonia (a World Heritage site) in Uruguay for the day and a trip to Tigre in the delta.Both are worth doing just to get way from the hustle and bustle for the day.
BA is a good destination to walk about in between taxi rides, so bring some comfy footwear. ^

Have a super holiday.