I am a US Citizen (born in Cuba), my boyfriend is a US Resident with a Green Card (born in Colombia) and we live together in the USA. We want to marry both in the US and Colombia but I have no idea what are the requirements for us to get married in Colombia. Any comments would be greatly appreciated, I would hate to get to Colombia and not be able to marry.

You can only marry "once" the other service would not be a actual wedding.

So you get the marriage license at or for the wedding you want to be the real one, the other is just a service, blessing the real marriage.

As for as being "married" once you are married in one place, you are married in all places, ( with exception of pural or same sex marriages)