The best place to sit on the lower level is in a place that gives both a good angle toward the stage and is also not too far away from it. Sections 111, 112, 134, and 135 are two sections on each side of the stadium that are in great locations to watch the concert. These sections are the closest to the stage that are angled the right way for a concert. It would be better to sit in these sections than some on a higher level because they are much closer to the stage, but it would be a good idea to sit in a row near the middle of the section on the lower level to get some elevation to see over all of the people on the field.
It is important to avoid seats in the outfield (Sections 140-143 and 102-105) on the lower level because these seats are almost behind the stage and have very poor views.