David,
You might want to read the archives of alt.support.cerebral-palsy.
There's been tons of debate on there about the benefits of HBO therapy
on CP, and it seems like the jury is still out. There are people that
feel strongly on both sides over there, though. You might see if you
could write to a few of them and get some opinions. I myself don't know
much about it, only that there are no proven results. On another note,
I'm also 15. It's always nice to see someone my own age. Welcome!
~Joy~