According to this VJ Guide to Removal of Conditions... http://www.visajourney.com/content/751guide
You will NOT be sent any reminder to file this petition from USCIS. Per the USCIS,
"At the time you obtain conditional resident status through admission to the United States with an immigrant visa or through adjustment of status, the USCIS will notify you of the conditional basis of your status, the requirements for removal of the conditions and what will happen if you fail to file a petition to remove the conditions.
The USCIS does not send a second reminder to conditional residents to petition for removal of conditions. During the 90 days before the second anniversary of the date you obtained conditional resident status you and your spouse (if still married) must file to remove the condition."
This appears to have changed!! Just got a letter from USCIS today, "Notice of Requirement To File Joint Petition To Remove The Conditional Basis Of An Alien's Permanent Resident Status", saying...
"The records of this Service indicate that you entered the United States as a conditional permanent resident on 10/06/2011. In accordance with Section 216 of the Immigration and Nationality Act you must file Form I-751, Petition to Remove Conditions on Residence. Failure to do so may result in the automatic termination of your Status. You can obtain Form I-751, as well as filing information and fees, from www.uscis.gov or call 1-800-375-5283."