Denver: Best area in Denver for younger crowds & good nightlife?
LoDo, River North Art District, and the Highland Crossing have fun restaurants. 16th Street Mall is OK if that's your thing, but it's just a mall.
Denver: Weather in Denver?
Pretty dyslexic. It can be 70 or snowing. Usually pretty mild, though. Check the forecasts ahead of time and come prepared, particularly if you plan to visit the mountains.
Denver: What to do in Denver, CO?
Microbreweries are great. Otherwise, there's the United States Mint (Denver Mint, check hours and reserve ahead of time) and some great museums. The Museum of Contemporary Art Denver is fantastic.