Steve, FWIW, I run a 180 T-stat with about 25% mix of
antifreeze and a 14 lb cap...my car runs at 175 on the road and 195 or so in Houston stop and go, in the summertime (90-110 degree ambient temp), and I almost never use the manual fan over ride (and then only when traffic is stopped or during tuning). I'm about 15 miles west of you, and both here and further south, the hottest it's ever gotten is about 215 during extended idling during carb tuning or the like. Absolutely NO overheating problems, and not really any problem "burping" the system.
I don't want to be flamed for this, but I don't think the suggestions from SA are the answer. Their suggestions are good for racing or hard use applications, but in your case (street use) they seem like bandaids, not cures, since your setup and mine are very similar. I'm with Ernie, I would not run more than a 15 lb cap for street use, and wouldn't run a restrictor or a T-stat lower than 180 (except while you're looking for the real problem, that is). Once your system is sorted out, the 80-92 degrees would be right for Houston, regardless of the ambient temperature.
Please let us know what you find.
Oh, and one other thing, not likely...a plugged up exhaust can cause overheating too, are your pipes breathing okay?