Denver Colorado Bus SystemsRegional Transport District of Denver, Colorado.
Extended information on Denver ColoradoPopulation as of July 2009: 610,345.
My town is 50x bigger than yours, 12th the size of Denver. I feel more relatable to yours, though due to our rural background. The plus about big cities is that, due to the size, they like to shove a LOT of things into grouped areas so walking can be an option. It's common in some cities for people to not own a car at all because public transportation is easier. I took a trip down to Boise (3rd the size of Denver) and there were so many people walking places because it was more convenient than being stuck in traffic.
You
should stick to buses, unless you're only travelling short distances. With the bus, you can get a map of the area! ;D Google Map your hotel and take down the places you'd be interested in, then print out the map on your computer and/or mark them on the bus route when you get one. Feel free to be curious, but treat it like Las Vegas, don't let anyone you don't know know that you're visiting and are new to the area.
You'll definitely become a big city pro in three days!