Unfortunately the period of time to process the I-526 petition is unpredictable and we can only estimate the processing time for the approval of an I-526 petition and then furthering the process by applying for conditional permanent residency, usually through the U.S. consulate. In certain circumstances, our Law Firm has received an approval of an I-526 petition within two months, but of course we cannot guarantee that this is going to be the case with all filings of an I -526 petitions. Recently the processing time for an I-526 petition might be 12 months more or less.
As stated on the USCIS processing time web page, the last processed I-526 was in March of 2012. Our understanding is that current processing times are approximately 12 months.