The integrated luminosity for validated runs and luminosity sections of the 2011 public data (RunA) is available in the table 2011RunAlumi.txt. (The integrated luminosity for validated runs and luminosity sections of all 2011 p-p data taking is available in 2011lumi.txt.)
In your estimate for the integrated luminosity, check for which runs the trigger you have selected is active and sum the values for those runs. The uncertainty in the luminosity measurement of 2011 data should be considered as 2.2% (reference CMS PAS SMP-12-008).
If you are using prescaled triggers, you can find the HLT trigger prescale factors for different run ranges in trigger configuration files listed in this record (under "PrescaleService")