Steve,
The Winter Texan area of the Rio Grande Valley runs from Rio Grande City in Star County to South Padre Island. Most of the RV parks are located from Mission to San Benito, but there are others outside of this area to the west and east of these towns. If you want to explore the area the best location in in the middle of the RGV which is the eastern part of Hidalgo County. That is where Donna and Mercedes are located. The RGV is very long and narrow so a trip from one end to the other and back is over 150 miles. VP and Llano have one location each and both are located right in the middle of what the valley has to offer in the way of events and things to do.