Being a semi-regular to the Denver area, I have compiled a list of some yummy restaurants for those heading to this year's GABF.
My personal favorite is Osteria Marco. It's pretty rustic Italian food. They make great homemade ricotta and mozzarella, suckling pig roast on Sundays, grilled artichokes and rocking pizza with a runny egg yoke on top. The prices are reasonable and the service is spot on. If you eat at one spot, this should be it.
For happy hour, McCormicks (I know it's a chain) is quite good. You can get a bowl of mussels and a salmon cake for under $10. The late night happy hour is great after sampling a bit too many brews. Or you could go across the street to Jax and eat some fine oysters and some pretty good fusion food.
The most recent place we groove on is the 9th Door. It's a tapas bar. So if you want to eat a bunch of small bites, it's a great place to go.
For breakfast, I love to eat at The Bagel Deli. Once in a while they'll have a Reuben omelette that might sound gross but somehow works really well.
That should get you started.