You could also fly to Guadalajara, which is Mexico's second largest city, and where there are more flight options. From there you could take a bus (30 usd), which will take 3 hours to get to Colima bus station and from there to the down town a cab will charge you 2 or 3 US dollars.
'''Sleeping'''
You can sleep downtown in the Hotel Ceballos ( Best Western )or Hotel America, just out of the downtown you find the hotel Maria Isabel and at the edge of town is a Fiesta Inn.