Cowboys- check
Dinosaurs- check
Space Colonies- check
laser rifles- check
Cute blondes- check
Its a winning formula
All-in-all, it's a winner. I have a question though, how big are these brontos? You mention them being 3-tons, but then one gets hitched to a wagon like it's nothing.
In this case 'wagon' is a colloquialism, in the same way that a modern-day construction site's 'chuck wagon' isn't actually a covered wagon. On New Texas, a 'feed wagon' is a large, diesel-powered crawler that serves as a central post and feed supply, and is about the size of a small building.
Also, how big is a diablosaur? Are these creatures much different from Earth-dinosaurs, or did they just get named by colonists who had no other words for them?
A diablosaur is a bit bigger than a SW taun-taun, and is also bipedal. To answer your second question, I should provide some backstory;
In my universe (the same universe as my
Scattered Earth series), there were a number of large, sleeper-style colony ships sent out as a part of 'Project Destiny'. Big ships with 50,000 colonists were sent out to different star systems in the hopes of finding new homes for humanity. Earth was devastated shortly thereafter in a nuclear war, and the colonies were largely forgotten. New Texas (settled largely by north-americans) is actually Epsilon Eridani III, an arid world capable of supporting its' own indigenous life. It has no large mammals, but instead endothermic dinosaurs. The various beasties were named, tamed, and domesticated by the colonists, and were simply given appropriate names.
There's a 2nd colony in the system, a cool moon orbiting Epislon Eridani IV, dubbed 'Yukon'. There the remaining 15,000 colonies settled and started their lives. There is limited travel and communication between the two colonies, as they're still trying to get their industrial level up to large-scale spaceflight. This story is set 150 years after landing.