I believe this choice is to determine where most of calls/texts your will be made to. Choosing Home will designate your home area code as your most frequently called area (no roaming charges) while Travel will probably allow you to choose a different area code as your most frequently called area. When you call out of your chosen area code roaming charges apply. Example, if your current phone area code is 123 and you move to area code 321 you may want to change your Home or Travel designation depending on where most of calls are made to since you can't actually change your phone number.

As for your other question, you don't need wi-fi to text. It's like making a phone call, you simply choose message instead of dialing a number. Phone calls cost 1 unit, while text messages cost .30 units. (Units are the dollars you spend to buy minutes divided by the total number of minutes you receive) Hope that helps.