I believe its the same months every year, that would make it June,11 to August 11 as the months one has to be there in SF for the Summer 2011 cycle.
Regarding the start and end of the application process, assuming it would be started and ended with the same lead time as the winter 2011 cycle, the start and end dates would be:
Start - Mid Jan 11
End - Mid Mar 11
These are just guesstimates assuming that YC repeats the same pattern every year. It would wise to keep checking HN to see if they indeed do that.
Regarding the start and end of the application process, assuming it would be started and ended with the same lead time as the winter 2011 cycle, the start and end dates would be: Start - Mid Jan 11 End - Mid Mar 11
These are just guesstimates assuming that YC repeats the same pattern every year. It would wise to keep checking HN to see if they indeed do that.
Good luck. Skowmunk.