Try the CSU Oval for a Ceremony
The Oval is a beautiful location for many students that have attended CSU and has special meaning and can be very inexpensive.
Also the campus has event centers for receptions.
Also City Park in Fort Collins or a host of other parks in the area and beautiful.
If an indoor venue is important try Barn Weddings it gives a rustic feel and can be a lot of fun. and the reception can be hosted there as well. check with local farms just outside the city limits.