http://www.pparc.ac.uk/Nw/marsis.asp
http://www.space.com/news/mars_water.html
http://www.marsdaily.com/news/marsexpress-05f.html

Here are some links which should shed some light on the subject. While you may be correct, I think you are only making an (educated) WAG, and like the rest of us have little idea what they will find and what will be the nature of the radar signal information. That is the whole point of the RADAR sounding and the excitement about it. WE DONT REALLY KNOW WHAT WE'LL FIND.

Some notable quotes from the links:
first contradicting your initial statement radar--> only liquid water
"Radio telescopes on Earth then looked for the radar reflections, detecting stronger returns where ice crystals were present in the soil."
talking about radio dish analysis of moon craters.
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Yes. Liquid water is much, much more reflective than ice. Ice is actually intermediate in its reflectivity between soil and solid rock. So it may be difficult in some cases for us to detect interfaces where ice is present and ice is absent. But until we start doing the experiment we won't really know how hard that is.
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The prime objective of MARSIS is to map the distribution of water and ice in the upper portions of the Martian crust. Using techniques similar to oil prospecting on Earth, the instrument will analyse reflections of radio waves in the upper 2-3 km of the Martian crust to reveal the subsurface structure. It will be able to distinguish between dry, frozen and wet soil.

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The above were not really technical, so here is a more technical abstract about SHARAD which specifically speaks about searching for ICE with RADAR.

http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003EAEJA....13385B&db_key=PHY
Abstract
The SHARAD (SHAllow RADar) is a radar sounder that will be used to explore the subsurface and surface of Mars in the context of the Mars Reconnaissance Orbiter 2005 mission. The subsurface sounding radar SHARAD will be capable to detect liquid water and to profile ice in the first few hundred meters of the subsurface at approximately 10 to 20 m vertical resolution (10 MHz bandwidth; 15 m resolution in free space). The horizontal along track resolution shall be approximately within the 300 m-1000 m range while the cross track resolution shall be within 3 to 7 km. The primary scientific objective of the SHARAD investigation is to map, in selected target areas, dielectric interfaces to depths of up to one kilometer in the martian subsurface and to interpret these interfaces in terms of the occurrence and distribution of selected materials, including rock, regollith, water and ice. Probing the upper crust of Mars with radar in the 10 MHz frequency range is a unique way to study the planet, compared to all other investigations completed, in progress, or planned for the future. The only instrument comparable to SHARAD, which will be placed in orbit around Mars, is MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding), on board ESA Mars Express spacecraft. The penetration depths expected for MARSIS, up to 5 km, will open up a new realm in the study of Martian crustal properties and geologic processes. MARSIS, however, has a relatively coarse resolution, and was conceived to test hypotheses on global models of subsurface water and ice distribution. New results on the distribution of subsurface water on Mars, brought by MGS, have prompted the need for an instrument complementing the results of MARSIS. An instrument able to penetrate a few hundreds of meters below the surface with a finer resolution would provide a unique insight into the Martian stratigraphy at scales comparable to those of optical images. Unambiguous detection of liquid water and ice reservoirs will require mapping the presence of discontinuities and studying their correlation with depth, latitude, surface topography and local geologic units. Such analyses will also address a secondary objective of the Mars Reconnaissance Orbiter mission, which is to utilize subsurface probing to map geologic units and structures in the third dimension. An additional secondary scientific objective is to characterize the properties of the surface of Mars by operating the SHARAD as an altimeter. This will generate a new topographic data-set for Mars at a resolution better than 1 km.