It's actually not a "dirt lot" anymore. They paved it last summer, thus eliminating the problems of flooding and some of the icing problems. It is known as the "Cannon" lot. Parking in this lot requires a "C" permit, which last year cost $201 for the year. I'm sure it will go up another $5 - 10 this year. A "C" permit also allows you to park in faculty lots (A and B permit lots) after 4 pm and on weekends (nice for evening or weekend studying in the anatomy lab or library). If you look on the map found at
http://tp.osu.edu/maps/hospitalparkingmap.pdf, the lot you are referring to is the big green area towards the top of the page. (Green areas are C permit lots). It looks like a hike from the lot to Meiling Hall (building 281 on the map), but its only about 5 - 10 minutes. If you plan on living in Grandview, this will be the more convenient lot. The other "C" lot on the above map looks a little closer, but it is considerably smaller and much more of a pain to get to than the Cannon lot.
Although you can ride the bus for free (which some students do), COTA is not all that user friendly - most busses only run every half hour to every hour, so if you just miss your bus, you can be waiting awhile for the next one.