Coming from the wilds of Canada, I'm used to bushwacking. "Bushwacking," means just pushing your way through plants and trees and making your own trail where there wasn't one before. Well, you can't do that sort of thing here because the flora bites back! And it hurts! Every single plant seems to have its own spiky defenses--cactus, aloe, and trees are all covered with thorns.
Out of habit, I brushed a harmless looking leaf out of the way and was rewarded with a giant scratch down my arm which bled for a half-hour. It was a painful act that I was to repeat several times over the coming days no matter how much I tried to remind myself of the danger. It's probably not a good idea to cut your own path through these plants anyway because the creatures lurking under them (rattlers and scorpions) are far more dangerous that what you may be used to.
Bring some Polysporin (antibiotic cream) and Band-Aids (plasters), because you'll probably get attacked by at least one deadly greenery during a desert romp.
When hiking, watch out for prickly cactus. Wear thick-soled hiking boots and avoid backing up to take pictures on nature trails, or you may find yourself picking hundreds of tiny thorns from your leg, which can be quite a nuisance!
Don't run across this type of sign every day. Good advice though, coyotes are perfectly capable of finding their own dinner. Let's just hope that it is not Uncle Mike's pommeranian that ends up as the meat du jour.
I was told this by more than one local - They shake their shoes out before they put them on in the mornings, just in case. Scorpions *do* live in tucson, so it's not an unheard of thing to think they could get into your house. I was initially skeptical, but when the second person I talked to suggested it, I really started to pay attention.