you are allowed to carry a firearm in your vehicle (concealed or visible)
Incorrect. A pistol in your vehicle must be concealed.
Be careful in City of Houston. Absent a CCL, LEO in several areas of town have been instructed to arrest anyone with firearm in their vehicle even though it's not against the law...to let the court make the decision.
Just don't get pulled over, be respectful, keep your weapon concealed and don't disclose that you have a weapon.