Absolutely beatiful hiking area. The Gateway Loop in particular is my favorite. It really takes you away from the noise of civilization and back to nature. It's not too strenuous, and definitely dog friendly. On the weekends, it does get very packed with walkers and runners alike, so be aware of your surroundings.
Something very special about the trail head is the educational nature walk they have installed. There are about fifteen stops along the path with information about the plant life, animal life, weather, ecology and human interaction with and of the Sonoran Desert. Im glad I took the time to check it out because I definitely learned a lot about the desert that I hadn't known before.
Highly recommended way to spend a few hours.