Determination of B(J/psi -> l^+ and l^-) and Experimental Study of psi(2S) to pi^+ pi^- J/psi Using a sample of 3.79 M Psi(2S) events, the J/psi leptonic branching fractions are determined from a comparison of the rates for psi(2S) -> pi^+ pi^- J/psi, J/psi -> l^+ l^- and J/psi -> anything. The results are B(J/psi -> e^+ e^-) = (5.90 +/- 0.05 +/- 0.10) % and B(J/psi -> mu^+ mu^-) = ( 5.84 +/- 0.06 +/- 0.10) %, where the first error is statistical and the second is systematic. The events are also used to study the process psi(2S) -> pi^+ pi^- J/psi. The dipion mass distribution peaks at high mass, which is different than what is expected from phase space. Tne angular distributions indicate that the dipion system has a small amount of D-wave. The dipion mass distribution and angular distributions are compared with heavy quarkonium models.