  We probe the strength of electron-electron interactions using
magnetoconductivity measurements of two-dimensional non-degenerate electrons on
liquid helium at 1.22 K. Our data extend to electron densities that are two
orders of magnitude smaller than previously reported. We span both the
independent-electron regime where the data are qualitatively described by the
self-consistent Born approximation (SCBA), and the strongly-interacting
electron regime. At finite fields we observe a crossover from SCBA to Drude
theory as a function of electron density.
