There are places just off the Ramblas that are ok for prices( for Barcelona). Just go through the accomodation choices and look for proximity to it. We stayed further away - able to walk to the centre but I think you may want to be closer. For nightlife- too old to help you with that! Good time of year to go. Tapas all over the place- its great as you can graze all day long and not bother with dinner if you want- can help soak in the alcohol as well