Saturday has the highest chances of anyone more than an hour away coming, as you said. Don't know why you're even asking people's opinions on that one.
As for the rest, if you want it to me a large tournament, the only thing you need to ask us for is support. No matter how good of a TO you are, you -will- need support to run a large tourney, but I think you'll have more than enough support from the LA community cause..well...we're awesome.
So really, the only questions you need to ask are "Are you up to organizing, promoting, and running a large scale tournament?" and "What weekend would be best for OoS attendance?" Need to avoid scheduling it near other big tournaments. Avoid Phase Weekends, avoid WHOBO months, should probably try to avoid HOBO weekends, but attendance to those seems to be dieing. You'd probably need to look at tournies in the South West as well, depending on how big you want this to get.
Oh, and March 13th is probably way too early if you want more than just part of Texas to come.
I'm sure this is all stuff you know already, but just pointing it out in case it slipped your mind.