I suggest Cherry Creek. Its relatively near the tech center area and its a fairly good neighborhood in Denver where you can do the things you mentioned - walk to coffee shops and clubs with pretty decent music, there's a terrific independent bookstore called the Tattered Cover and you also can walk to a huge city park and the Denver Botanic Gardens. I used to live in Cherry Creek and liked it a lot.
Boulder is a fun university town, but VERY expensive. However, if you are used to Cali prices, you might actually find Boulder reasonable.
Avoid Colorado Springs like the plague unless you are right wing, fundamentalist whacko in which case you'd feel right at home!
