Weed is technically legal, but not really up for purchase until January. Not much has changed, everyone I know who buys still needs a med card to do so. I guess there are a couple bars where you can go smoke, but I think you need to bring it yourself. We're not quite the Little Amsterdam that everyone thinks we are... yet anyway.
Where to stay? Dick's Sporting Goods Park is near a cute suburb of Denver called Stapleton. There's an Embassy Suites there. It'd be a lot closer than staying downtown, so if you're cabbing it to the show, that'd be a good bet. You're still pretty close to Denver, if you want to co explore there.
As far as where to hang out, I'd suggest the Capital Hill area as opposed to downtown Denver. I'm particularly partial to City O' City, a pizza place there with an interesting drink/food menu.
Another place I try to take anyone who comes to visit is called Pints Pub. If you enjoy single malt whiskey, you must go. Largest selection in the US (possibly anywhere outside of Scotland). The food is great too.
When the stars exploded billions of years ago, they formed everything that is this world. Everything we know is stardust...