Sure do.
The first, best way is to speak with your guidance counselor at school and find out of they know who the ALO assigned to your school is. If they do NOT know, then pm me (flieger83@cox.net) with:
School Name, Location (City, State, etc.)
And I can look them up.
As for when you should contact them? It wouldn't hurt to drop them a note as a sophomore to let them know you're interested in all things USAFA. That would give them at least your contact information. They won't become too involved with you until the Junior year.
You should, at the same time, start looking to see when your congressman and senator are holding "all academy days" or similar functions and go to them. You'll get to meet ALO's, Blue and Gold Officers (USNA) etc...etc...and can get a LOT of information there.
Also...go onto the AFA website:
www.academyadmissions.com and fill out the pre-junior database contact information.