Saturn's moon Enceladus is thought to possess habitable conditions due to the presence of a global ocean, potential water-rock interactions at the ocean's base, and its ocean composition derived from sampling active plumes at the south pole. The thin (<35 km) and cold ice shell of this small moon in the outer Solar System is expected to allow the direct detection of the ice-ocean interface using low-frequency radar sounder instruments. Here we investigate the two-way radar attenuation in Enceladus' ice shell, focusing on the effect of a porous icy layer generated by Enceladus' jet activity. Our results show that in regions with a thin (or absent) porous surface layer, total ice shell penetration is possible. In regions covered by thick and strongly insulating porous surface layers, however, as little as 2% of the ice shell can be penetrated. Nevertheless, a thick porous surface layer leads to high subsurface temperatures promoting the formation of brines at shallow depth that can be detected by future radar measurements.