I lived in Houston right before I moved here, so I know the water is too hard, you will have dry spots if you use it for the washing, but will have no problem using it for developers. As a matter of fact in some ways it is good to use hard water as it contains Calcium Carbonate, which acts as a buffer in the developer. Dont waste your money on DI water, you wont see a difference.
I dont presoak, as far as I am concerned presoak is good for rotary developing to prevent surface tension from creating running channels, but I have had no problem with brush developing without presoak with Ilford FP4 and 400 TMY.
As they say your milage may vary.....have fun.