IMHO - This has been a great thread with great contributions.
We each learn and do things differently and of course, after reading lots of great
advice you will have to distill what works best for you.
I grew up on sailboats from age 4 and learned about sailing on a 22 footer and my dad and I built my first 8' sailing pram at age 6. I will say that in my mind, experience sailing small
boats is hard to beat. You learn quickly from
mistakes and really feel what sail and boat trim can do. I agree with all that an easy to tow sailboat is a great way to go. I'll put a minor
plug in here and even suggest getting a kit from Chesapeake Light Craft and build a sailing dingy like the Passagemaker. Build it over the
Winter while you take some online and classroom lessons. While
learning to sail you will also get a lot of boat care skills, and knowledge of a boat that few get unless you build one. The kits are easy, you could even take the course and build one at the CLC shop and tow it home but that's a bit much with you 1200 miles away.
In the mid 80's I sailed all over the lakes you mention and more, Grapevine is nice daysailing too. I took my Holder 14 all over there, Lewisville, Texoma, some other small lakes in Dallas and on the Chesapeake when I moved back here. You'll find lots of time to sail in Dallas with its not too bad
weather and build your experience.
Go
charter, a weekend, a week and do it several times. See if you really like cruising short term.
When I taught at
Annapolis Sailing School in college we had a nice mixture of courses, week long and weekend on Rainbow 23's. Weekend and week long on
Annapolis 26 and
Morgan Out Is. 41's. Lots of people took the week long
day sailing course then the weekend cruising and some bumped to the week long
cruise. About half the folks decided they liked weekending, about a third liked daysailing only and the rest never came back or went long term. You might want to look at what schools offer in this mixture.
You take
classes and get a lot of knowledge but sailing is one of those things that requires bruises and scrapes to really learn and do.
It's one thing to read about and have someone explain things like apparent wind, it's another to feel it.