I live in Fort Collins, and I will probably be going to CU. You can get by without a car, but I wouldn't recommend it. The first year would be fine, but if you are going to get a job, lots of the bus routes could take you a full hour or more of switching between bus lines. As far as the 4wd goes, you need it in this state about 8 times a year (probably actually less). So, if you can manage walking for those 8 days, get a car. The majority of people here have cars. Its a common misconception that Boulder is in the mountains right next to Denver and Pete Coors' beer brewery.