We overnight in Van Horn quite often - at Van Horn RV Park. It's a nice park at a good price (former KOA), with full hookups, a cafe, and 2 dog runs.
Perhaps these towns are against boon-docking to prevent the town from looking like a homeless camp. Seen that in San Diego; dirty broken down hulks that people have parked on the city streets. To me boon-docking is far from town, far from everything and not done in town when there are RV parks nearby.
2014 Voltage 3600 toy hauler
2013 Chevy 3500 dually
2011 Harley Ultra Limited