Firstly, welcome to the free state. Please check out the mountains and the hiking. I do recommend a good pair of shoes and prepardness. The people you will find are generally friendly. The traffic in Denver takes some practice to become safe around others. I really hope you enjoy what we have.
I will assume you take a cautious and non-confrontational stance. Generally, the library is ok, no display of firearms. (conceal). I have not checked reciprocity for Texas. Denver City and County prohibit open display by statute. I believe open display is not prohibited in city, state, and national parks. Carrying inside federal buildings is not permitted by federal law. You will see signs. I do not recommend openly carrying a shotgun due to the lack of muzzle and trigger guards. Please pay attention to business signage, it may save you headache. If you conceal in a business with a sign, I would try to make an effort on that. We will not win the advocacy movement by bringing a business into our message. They are concerned with profit, and generally not our second amendment. I have attached an info paper. here... colorado.pdf
The cog railway will tell you that they don't permit a weapon (may tell you) Generally I conceal in places without signs where employees are confused. This may not be the choice or recommendations of others, however.
CiCis pizza is good food, and gun friendly as was my experience. Target and Starbucks are not. Please stay safe and legal.