I heard a news anchor last night say they'd been told both that the dive team was training and that they received a tip, but had been unable to confirm. I haven't checked all of the updated stories this am, but I think that the dive team has done training exercises there before.
Also, you can get to Saraland from both directions of the interstate. If you took the interstate to the left, it would have been interstate until the Saraland exit and multiple exits could have been taken. If she took it to the right then she would have traveled through Downtown Mobile and eventually gotten back on the interstate. The latter being probably the slower of the 2 routes because you have to deal with traffic lights, slower speed limits, etc.