I'm not from Central Texas, but here's my 2 cents anyway...
There are advantages and disadvantages to formal organizations.
The biggest advantages I see would be in dealing with other
organizations - government agencies, the media, etc. A
formal "organization" will tend to have more influence than a bunch
of people who happen to be interested in the same things. An
organization doesn't have to be overly organized. NTGA still hasn't
defined what a "member" is, and has no finances or by-laws (yet). We
do have a website (www.ntga.net) that is voluntarily run, and we do
have officers, although we haven't defined what they actually do.
The biggest disadvantage is often that the organization sometimes can
get so big and cumbersome that it forgets what it's there for.
Politics and infighting can cause problems.
Decide for yourselves how "organized" you want to get. Or, sit back
and watch as NTGA and other geocaching clubs evolve, and then decide
what you want to do.