I understand this worry, and when I started college I had to make a choice like that. I ended up going to a college where I did know people, and honestly none of those people are my friends now. No matter what, you're going to meet new people, and you may not keep the people you had in your life from high school. Going to school with people you know is a good vehicle to meet new people so you don't feel alone, but you should go to clubs that interest you and campus events to meet friends.
Don't be afraid to just walk up to people and introduce yourself. You may be surprised with the connections you make.