How does a green card holder apply F2A visa for wife or should wait for US citizenship?

It is current that the F2a category will be current and therefore whether your husband becomes a citizen should not affect the waiting time. However, you must be clear as to whether you are eligible to adjust status. The manner you entered the U.S. and/or whether you were a beneficiary of a previously filed petition are questions that should be addressed to an attorney before filing.

You should file the petition right away instead of waiting till your spouse becomes a US citizen. Under current visa bulletin Aug. 2013, visas are current in the F2A category.

Yes, your husband can file a petition on your behalf but waiting time depends on USCIS processing times as well as Department of State Visa Bulletin. You are right about F2A being current for August 2013. It means that everybody who has an approved relative petition may apply for green cards right away without waiting in line for their priority date because this date is current for everybody. It is important to know your current immigration status in the U.S. If you are out of status, wait until your husband becomes a U.S. citizen before filing for anything. In order to obtain more precise information it is strongly recommended to seek formal advice from an immigration attorney who can guide you through your situation.

Processing times will be the same if you are in the US but you must be in lawful status at the time you apply as a spouse of a green card holder. You do not have to have legal status if you apply as a spouse of a US citizen as long as you entered the country lawfully. It takes about 3 to 4 months.