We have our share of ignorant inconsiderates, but I wouldn't say that Texans are not cycle friendly. I've ridden many, many miles in Texas and rarely have any problem. There are few bicycle specific facilities in Dallas, but people are generally neutral.

However, there are lots of rural roads, especially out near Decatur. Farm to Market roads (labeled FMxxxx) are often great roads for cycling. Lots of these are low traffic but well maintained by the state. Be careful about planning routes using county roads (labeled CRxxxx) as these could be anything from paved to oil top to gravel/dirt. You usually can't tell from a road map either. They can be great if you bring an MTB or know which are in good condition.