I don't know about Altamonte Springs, but from the airport to port takes us about 40 minutes. It takes us about an hour to 75 minutes to drive from the Disney resorts to the boat.
If I were leaving from the airport I would want to be picked up no later than 10. Getting to the port by 11 seems to work well for us, lines aren't generally too long and you don't have to wait for them to begin boarding for more than a half hour or so.
Mark