I know there are some Denver-ites that may like some places better, but I absolutely love:
1. The Blue Bonnet for lunch / dinner
457 S Broadway
Denver, CO 80209
Get a beef chimichanga and a Sun Shine Wheat, Fat Tire Amber, or take your choice of Mexican beers.
Matter of fact I highly suggest just having a sun shine wheat w/ a lemon, and a Fat Tire at as least one of your meals. My two favorite local beers, although New Belgium Brewing has grown a lot the last couple of years.
Another Place I love is:
Illegal Pete's
1530 16th St
# 101
Denver, CO
The big fish burrito is great, as well as normal steak and chicken burritos. I practically lived off of their burritos in college, and still catch myself dreaming about them occasionally.
If you go to Boulder, go down to Pearl Street. The Hill has been killed, unfortunetly. Used to be full of Bars and good times, now there isn't much left to do up there. At least that was the case the last time I was there 2 years ago.
Rocky Mountain National Park is about an hour away from Denver that would certainly be a nice place to visit, if you like scenery. Depending on when you are going the aspens may be getting close to turning, which can be a spectacular weekend in the mountains.
There is a shelby cobra museum somewhere just outside of Boulder, Co too. I've never been there though to give you a full report on it.
http://www.shelbyamericancollection.org/index.html
The performing arts center in Denver is supposed to be one of the best outside of NYC, if you are into that type of stuff.
Don't know if the CU buffalo's have a home game while you are there, but you could probably get tickets if you wanted to.
Or you can see about trying to find Grady Clay he is good for a couple hours of stories I'm sure.