I suspect it would be an extremely bad idea for Jeb Bush to call a simultaneous special election to fill the remainder of Foley's term. Many voters would skip Foley's name in the general election for the next two years and vote in the special for his replacement, thinking they got it all covered. If votes for Foley are to be votes for someone else then they should just name the replacement ASAP and run with that.
I'm pretty sure the same stategy is being used in Texas. Gov. Perry called a special election to fill Delay's seat to coincide with the general election where the GOP candidate is a write in
If they are already motivated to turn out for Katherine Harris in the general election, you'd make sure that they're educated about the whole ballot. Usually, the House seat is just below the Senate seat on Federal section of ballots. It would be hard to skip it.
Maybe even get Ms. Harris to explain how to vote in that district.
-PJ