How should a Canadian prepare for the SAT/ACT?

I'm 18 (graduated high school last June) and I spent the last year living abroad in Russia. While over there, I decided I want to go to school in the USA. I got good grades in high school (although math wasn't exactly my strongest area) and the Alberta education system is really good so I feel like I wouldn't completely bomb the SAT or ACT but I do know I still need some sort of preparation. I purchased the college board guide to the SAT (even though I think I'll probably end up taking the ACT.) Having said that, which test do you think I should take? I want to apply to BYU or Utah State so I'm assuming the ACT would suffice? How much time do you think I need to practice or prepare for the exam? Any other tips or advice? Thank you SO much!