There is no need to take the bus. It's only a 5 min.walk from T5 to TB. The bus may take longer since it will go through T6 -> T7 -> Airport return -> T1 - T2 -> T3 -> TB (LAX is like a horserace track and TB is between T3 and T4).
So if the Delta flight is on time or no later than 30 min., there'll be enough time for you to even have a casual lunch.:)
