Gastropub/brew pub in Portland
if you were to do an eastside tour...Burnside Brewing has great and fancy food and delicious beer...Coalition has a great new ESB, and Migration makes my favorite Nitro Cream ale...and Cascade if you like fruit beers is one of the most interesting breweries, as porky pine suggested..
I also like the Hophouse, for food and beer, as they carry many local beers and they have fried cheese curds...but it is casual.
For a pub crawl in a fun neighborhood with lots of food options - you could take a cab to Mississippi on the other side of the river.
Start at PROST (near a food cart pod) and work your way down the hill. INTERURBAN (good food) and AMNESIA BREWING would be two other spots to hit up. There are tons of good food options on that street as well - Lovely's 50/50, Ruby Jewel Ice Cream, Por Que No...
For creative beer, the Cascade Barrel House makes some very interesting sour beers that you won't find anywhere else. I love the beers there, they are unique and delicious. It's right outside of downtown on the Eastside of the Willamette river and not an expensive cab ride but you should eat somewhere else if you're only in town for a couple of nights. There are lots of good restaurants close by with good beer and food. Pretty much everywhere in Portland has good good beer, I'm just trying to think of a Gastropub with "creative" beer and good food. I really like Spints Alehouse for their beers and food. They always have a good mix of local and imported beers on tap and their food is really good. Neither one of these places are downtown but they are easy to get to with a taxi or on a bus. I can't really think of a really good example of a gastropub in Portland, it seems like the better brew pubs focus on their beer and the food is kinda like an afterthought. But most of the good restaurants here have a thoughtful beer list with good beer, just maybe not creative. Sorry if that's confusing, there are a lot of options for good beer and food, what kind of food do you want to eat?
I'm going to go out on a long limb and suggest vs. recommend Bailey's Taproom. Why? Because it's not a chain, it has local atmosphere, it has a decent assortment of both draft and bottles, it's downtown, and it's right across the street from Tugboat, probably the closest thing you'll get to a 'brewdive'—worth stopping by for that "you'll never believe this place in Portland we went to" experience if you're into that sort of thing.
Food is from Santeria, I believe, which is supposed to be Portland's best Mexican restaurant, though I can't vouch for it personally.
Bailey's is close enough to downtown hotels (about 2 blocks north of The Benson) that you can check it out quickly on your way to somewhere else to see if it's the kind of place you want to spend some hours in during your short stay in Our Fair City.
Without knowing more about your demographics and expectations, it's a bit hard to narrow the choices down better. I would recommend having a second choice if Bailey's turns out not to be your cup of tea, so to speak.