Given the cities involved, I'd say there's a good chance we're talking about Southwest (that or Continental). If it's Southwest, then you still can't get on in HOU if you skip AUS-HOU, but you
can get off your MCO-HOU-AUS connection at HOU on the return, within the airline rules.
And since Southwest generally prices all their flights as one-ways anyway, this may be a way for OP to save some money on the return leg. Note, they still won't short-check bags, and some reports are that your RR2 points won't post until you complete travel.
See
http://flyerguide.com/wiki/index.php...ack_tickets.3F