I've stayed at Tierdrop RV Park numerous times, usually for the whole winter. It's a decent enough place and owners are nice.It's easy to reach off of the Interstate. If you're travelling from the east be prepared to make a quick left turn as soon as you turn right from the ramp. There isn't much to do in Wellton, but it does have amenities such as a library, two grocery stores and some eateries. Of course, Yuma is only a few miles to the west.
BTW, there's a very new RV park just east of Wellton. It was just opening up when I was in the area a couple of years ago. I don't remember the name, but maybe you can find it on the Internet.
