Tim,
Mexico and IAH are not bad at all... Mexico is in fact some of the best flying and overnights that I've had since I started. All bases travel through each hub and all bases go to Mexico and Canada.
When you are on reserve then you are at the mercy of scheduleing... however once you have a line, then you can place your bid preferences into the scheduling program and bid around Mexico flying if you think it't really that bad. For example, I have my bid preferences set to look for DFW/DAL/PWM/GRR overnights for me. DFW/DAL so I can spend a night at home in the middle of a trip, PWM because I have lots of friends up there, and GRR because that where my parents live. But you can set your preferences however you want... to avoid things or to look for things.
As far as the rumors go... everythings a rumor until we see it happen on our bid packet.
Bob