last time i discussed beer in the keys with my pal who lived there he was complaining that he can't find sierra nevada pale ale, soooo... ?
Haven't been to KW in a while, but Waterfront was the only actual brewpub in KW that was worth a visit. Sloppy Joes has/ or had Joe's Tap Room attached and had a pretty good craft selection. Green Parrot, as previously mentioned, aside from the beer, is a cool local's hangout. If you have time and you're driving down 1 from Miami or wherever, you'll drive right by Florida Keys Brewing in Islamorada. Definitely worth a stop. Skip Islamorada Beer Company.
Waterfront is fine if you need a craft beer and watch the tarpon. But there aren't really any hot spots for craft. It's a light lager and tiki drink kind of town but you will find plenty of craft beer scattered about. Prepare to be underwhelmed and hope to be surprised. General Horseplay is a legit cocktail bar.