What are the requirements for a US Citizen and a US Legal Resident to marry overseas and have their license be validated in the USA?

She is a legal USA Resident and has had her green card since 06/2011. She has been living here but also finishing her bachelors overseas (Ecuador). She comes back every 5-6 months to maintain her resident card in good standing, then after 1-2 months leaves to attend the next semester. We are both interested in getting married overseas (Ecuador) in February 2014 right after she graduates, but are not sure what are the steps to take legally because we don't to have to pay huge paperwork fees to validate the wedding in the US. We were thinking of having the ceremony and reception first. then she would come back, get a civil marriage license after the whole thing already went down abroad. Is this a good solution to not having to pay more than we have to in order to validate our marriage license?