We made the trek down southwest to try this place after seeing all the positive reviews. It ended up being pretty decent but not worth repeating the trip from downtown.
The chips and salsa were fine, in fact, the salsa was actually pretty flavorful. The fajitas were very enjoyable, but the accompaniments left a lot to be desired. The refried beans creeped me out a little, and my wife reported her guacamole to be quite watery at the bottom. They just didn't seem very fresh.
I had a pretty strong-ass Patron margarita, too. Although - and this sounds totally lame - the balance was a bit off. The tequila overpowered the rest of the drink. I know - that's the dumbest thing ever to complain about.
Overall, Juan's is pretty decent but not good enough to justify the long trip.