We've got Stan's No-Tubes in our tires. Just what it says: no tube, a little bit of gooey stuff, a different rim strip, a different stem. It's kind of a big production, but DH and I have been very lucky with the stuff! Now, we don't live in the dessert and don't have to deal with goat's heads (OMG!!), so I don't know how this would do for you. It sounds like Slime is similar in that it finds the leak and seals it up, and it sounds way less difficult.

I do think that a recurring flat is an indication of something stuck in the tire, or even the rim. Our bike shop buddy once had a rim with a bad weld that kept flatting his tire for him. Check it carefully, then check it again! Hopefully you find something and can fix it up perfectly really quick!

Namaste,
~T~