xenon and
big eejit have covered almost all the ground I would have done. But to reinforce :
7 Stars is our personal favourite when we get to Bristol, superb range of qualityh beers from good breweries always. The Cornubia, which we used to refer to as the 'The UKIP pub' what with all the flags, is nevertheless also pretty good for ale choices, and from memory isn't quite as bad flagwise as a few years ago -- plus the clientele seem mostly just normal beer appreciators anyway.
Not exactly sure how much time you and friends will have
Hollis , but the Commercial Rooms, Corn Street, is a much better Spoons than the one right by Temple Meads, often busy though. Nearby to this, and more tucked away, you have The Bank Tavern, which is nice, and always has unusual (if limited) choices -- plus always two scrumpies.
The Barley Mow (easy walk from station) won Bristol CAMRA pub of the year for good reasons, we're big fans. I've even seen Wiper and True on handpump there (very rare), and The Moor Brewery round the corner from it often send a cask version of one of their beers to the BM. Arbor Brewery in Bristol now and again feature a guest there too -- it's a Bristol Beer Factory-owned pub, and BBF do great beers, but they invite in the local competition also!