Also don't forget there are different styles, there is in the US three styles of Taekwondo, American Taekwondo Federation (ATF), International Taekwondo Federation (ITF), and World Taekwondo Federation (WTF). For many people that's confusing because ATF is cheaper and a little more watered down, mostly, i consider it lazy Taekwondo, then again, I'm biased toward WTF, which is originally from Korea, so is ITF, either style is good. Just remember that.
I don't know much about other schools, but most of the schools in Denver do run deals from time to time, it is all the matter of catching the schools during that time. I know the school near Southwest Plaza runs deals all the time. Its an ITF (International) one and the teacher there is amazing and wonderfully friendly. So basically he ran it by me that for adult classes at one time it was 60 dollars per month.