Taking the NCLEX in Texa

It doesn't matter. But you will be paying more money if you get licensed first in Florida, as you will have to then endorse your license to Texas.

You can give them an address for anywhere. There is no law that states that you must reside where you hold a license.

The simplest way is to apply for a TX license and forget FL altogether.
In addition to more fees involved, as Suzanne pointed out, it will be more red tape and will take much longer to first get a FL license, then endorse into TX.
It's a waste of time and money to get a license in a state you don't plan on working in.
You can apply for a TX license while you're still in FL, take the NCLEX in FL but get a TX license issued instead. The only thing that you will need to do after that is give the TX BNE your new Dallas address when you decide where you are going to live.

Go to:
www.bne.state.tx.us

They explain the application process probably a little better than most BNE websites do but you can always call them as well.

My residency is still officially in California, though my upcoming NCLEX-PN examination is scheduled on December 28 in the Dallas-Fort Worth metro area. You can take the NCLEX anywhere it is offered, regardless of your current state of residence.