RV Park: I’ve stayed at Isletta many times. You only have water and electric hookups. Their “dump station” is in constant need of a boatload of Draino! They close the gates at 6 PM which is challenging if you’re visiting friends in the area or the Balloon Fiesta. Their rates are cheap ($17 or $18) but the camping area is not lit. The roads are not well maintained and go every which way as do the campsites, so it’s hard to determine where you can/can’t go after dark. The night watchman is very nice and will come to let you through the gates. BUT if the gal in charge finds out and takes a disliking to you, you will find yourself on the “Do not camp here any more list”!
Overnight: Approx 5 miles south of interchange I-40 and I-25. Heard there are some elect. hookups but can't confirm. Free
Casino Camper Research: Thanks to the tip from Tony K. above I did some research on this one. Sounded like a good deal. And it seems to be. There's a lot next to the casino where you can park for free, and there are even a few electric outlets on a first-come basis. Reports vary from 4 to 6.
The Islata Pueblo area is quite large and includes the Islata Pueblo Recreation Area a fishing lake and RV park at the lake. Not sure how far this is from the casino