Hey hit me up when you're in town. I might be available to have a couple of pints. There's a few places that aren't terrible, although certainly nothing that really qualifies as a true 'brew-pub'. Second Street Grill has a pretty good selection of NW beers on tap and in bottle, stuff from in town, and Seattle mostly, with a few outliers. Bob's Keg and Cork (not to be confused with Bob's Burgers and Brew, a regional cahin restraunt similar to Red Robin and right off the freeway by the Fairfield Inn) usually has some great imports on tap and in bottles, mostly Belgians the last time I was in, and is within walking distance of Second Street. There's also Bert's Pub out towards West Valley, more of a sports bar, but they too have some decent locals on tap, and good seasonal selection too. Plenty of Wine to taste down town if you're into that, and most of the tasting rooms out in say Zillah opened last weekend. Most offer around 5 tastings, usually gratis.
As For buying hops, the drive to Mabton isn't too bad, 40 minutes each way, if you stay under 70... I'd just go pick up an online/phone order that way, and as others have suggested stop off at Snipes on the way. If you're mobile and it looks like you'll be heading down from up North, you could stop in Ellensburg and visit the Iron Horse tap room, or head bit West to Roslynn, the small town has a small brewer, with two taps. Otherwise Leavenworth for some German imports and a few locals, or Old School house in Winthrop.