Don, Rica does pretty good with the prickly pear. It is the cholla that I avoid hunting in. If she gets a cholla ball on her foot, she tries biting it off, and then it's a bigger problem.
Mearns habitat is more grass/oak/hills. There is just a little cactus. Hopefully the mearns population will recover some more and you can make your bucket trip next season. You might try rubber boots if your dogs keep getting cactus spines.