I'll be staying in Tarifa, Spain the last week of March. I need to get Barcelona on Friday, March 30. I know I have to get to an airport in Malaga to catch a flight there but I'm concerned on how easy it is to get from Tarifa to Malaga.
Probably should. The walk up rate for an airline ticket tend to be the most expense. And, unlike a train, airplanes did sell out and schedules are not as frequent. So if you need to hit a schedule then buy as soon as possible for best rate.
Buses from Tarifa to Algeciras take half an hour and run frequently. From there, you can catch a train (4-5.5 hours, with a connection) or another bus to Malaga (direct, 2.5-3 hours, multiple companies).
Or trains from Algeciras all the way to Barcelona take 8.5 hours with one connection, which sounds like the easier plan.
Looking Up Train Schedules and Routes Online gives you the Deutsche Bahn train schedule link and tips for using it.