My experience:

1) If you're driving an automobile, expect to waste lots of gas (maybe even more in Texas?).
2) Get there early, the bikes sell fast.
3) Wealthy neighborhoods do tend to have higher end bikes, but they're usually not bargains. Of course, this isn't a hard and fast rule. I've gone to estate sales at mansions with low-end gaspipe department store bikes marked at $200! No kidding.
4) Neighborhood or townwide sales will give you the most bang for your mileage buck.
5) Most of my best finds have come 'accidentally' at garage sales I didn't plan to visit. So if you have the time and inclination, follow random garage sale signs!
6) It's more about serendipity than planning. I've been to more garage sales than I'd like to admit. Honestly, with the time and gas money I've spent, I would have been better off paying premium ebay prices. My yard would also probably have fewer weeds.

But hey, what can I say, I'm addicted to the hunt!