We have studied the electronic properties of the 2D electron liquid present at the LaAlO$_3$/SrTiO$_3$ interface in series of samples prepared at different growth temperatures. We observe that interfaces fabricated at 650{\deg}C exhibit the highest low temperature mobility ($≈ 10000 \textrm{ cm}^2/\textrm{Vs}$) and the lowest sheet carrier density ($≈ 5\times 10^{12} \textrm{ cm}^{-2}$). These samples show metallic behavior and Shubnikov-de Haas oscillations in their magnetoresistance. Samples grown at higher temperatures (800-900{\deg}C) display carrier densities in the range of $≈ 2-5 \times 10^{13} \textrm{ cm}^{-2}$ and mobilities of $≈ 1000 \textrm{ cm}^2/\textrm{Vs}$ at 4K. Reducing their carrier density by field effect to $8\times 10^{12} \textrm{ cm}^{-2}$ lowers their mobilites to $≈ 50 \textrm{ cm}^2/\textrm{Vs}$ bringing the conductance to the weak-localization regime.