If you have a MBP with the HiRes 1680x1050 resolution 15" display, then the Resolve GUI should work properly. If your MBP has the standard 15" display with the 1440x900 resolution, then the Resolve GUI will not fit properly on it.
If you have the 1440x900 display, there is no solution to make the Resolve GUI fit on it, except, as you noted, if you are running OS X 10.6.8, in which case you can use the OS X "AppleDisplayScaleFactor" command to make it fit, which was removed in Lion.