Your son's story sounds very familiar....my son tore his UCL during the summer after his freshman year. After an initial misdiagnosis (and a few wasted weeks undergoing rehab that only worsened his condition), I brought him to Dr. David Lintner in Houston. His Tommy John surgery was in September of 2009. No pain afterwards,in fact, never took a pain pill aside from Aleve. He was in his brace 5 days post-op and began his first session of therapy that day. I drove him to therapy two times a week for 4 months, then dropped to once weekly for 4 more. He began a throwing program in January, so approximately 4 months post-op. Much to our surprise, they started him on a modified pitching program in April, just 7 months post-op. Of course, this was all done under the supervision of his surgeon and the rehab staff. They were surprised at how quickly he was progressing.
He was actually released for position play (LF,2B,or 1B)about mid-way through the season; however, his HS coach opted to have him sit the season out.(Prior to his injury, he was an OF/P.)
He was released to pitch from the mound in games this past summer under a strict pitch count (2 innings/20 pitches per inning max). Needless to say, HS coach was cautious, so he didn't get much mound time. He played fall ball this year on a great team and was able to get some decent (but modified) mound time. I'm a mom, so I was sure to let his fall team coach know what his limitations were and watched like a hawk to make sure they were followed.
Biggest drawback from the surgery has been trying to overcome the perception (in his mind) he has been "passed up" during his extensive rehab. He was finally able to show the coaches his speed, agility, and arm strength are still better than most players on the team, injury or no injury. The one downside has been his bat. It is evident that the loss of the at-bats he missed during sophmore season are almost impossible to overcome. Coach has basically decided he will be a pitcher only at this point, which is really his best shot at playing college ball anyway.
On a good note, his speed has increased since surgery. He was throwing 82-83 before the injury and is now throwing 87-88 (currently a junior). I believe it has mostly been due to the increased strengthening of his shoulders and back from all of the rehab work.
Everyone comes back at a different pace. My son still gets frustrated, as he feels he should be further along now than he is. I have to keep reminding him this is not a race. Staying healthy is the key. Good luck to you and your son during recovery!