The saturation performance of the IEEE 802.11 broadcast scheme in two dimensional (2-D) mobile ad hoc networks is studied in this paper. A simplified yet reasonable system model is built to derive the closed-form expressions of two broadcast reliability metrics, Distance-based Packet Reception Probability and Average Packet Reception Probability. Compared with the existing work in the literature, the proposed system model accounts for more general 2-D network scenarios, and considers both the impact of concurrent transmissions caused by identical backoff intervals and that of hidden nodes caused by a limited sensing range on a tagged reception. All the analysis results are validated by extensive simulations.