1. UA would be very excited to have a student from SD. While geographic diversity isn't a requirement for merit scholarships, it could give you a leg up when it comes to other programs.
2. Southerners are some of the most polite, friendly people you will meet, though I know that is also said of mid-westerners. Apart from the occasional "Yankee" reference (usually in conversations about the Civil War), rarely ever does anyone make a distinction between North and South. As long as you are willing to experience new things, you'll be fine. Coming from WA, people told me that there would be a lot of differences. Honestly, the differences proved to be small and more entertaining than anything.
3. I know quite a few people majoring in Poli Sci, including some on CC. I'm not too familiar with the Journalism department other than knowing that the associated PR
department is highly-ranked and well-liked by students.
As m2ck says, retake the ACT and also take the SAT (don't forget to study, lol). I don't know if SD or a neighboring state has the September ACT, but it might be a good idea to sit for that and possibly the October sitting too.
Out of curiosity, what made you decide to apply to UA? I'm always interested to hear people's responses.
Best of luck in your college search and feel free to ask us any questions that may come to mind.
*A Non-UA Related Tip: If you haven't already, take a look at the WUE program that's for residents of Western States (SD is one of them).