There are some cha charn tings (local cheap diners) on Minden Row, behind the Sheraton.
There are always Cafe de Coral - closest ones are at Star House across the Star Ferry, and Chungking Mansion on Nathan Rd.
Serenade, the Chinese restaurant run by Hong Kong's Maxim group, is at the Cultural Centre next to the IC. Dim sum starts at 9am. Not the cheapest, but definitely cheaper than the IC.