Amigo ... PNGames ...
Around that time frame ... end of Dec ... Cali will be in their Ferria or carnival time. Lots of fun ... but on the 31st and on for a week things are pretty dead.
I imagine most cities are more or less the same at the beg of Jan time frame ... chicas on vacation to see family.
I don't like those marriage agency sites ... I would rather meet chicas on Amigos.com or Latincupido.com ... I really don't even do that anymore.
You could try it though ... maybe pay for a few of the e-mail addresses ... see what happens ... remember those hot chicas prob get bunch of emails.
Go to Cartagena, Medellin or Cali and just talk with every hot chica you see ... be funny ... make them laugh ... it's so much more excepted there than in the USA.
Get invited to a party and you'll meet muchas chicas lindas in whatever city in Colombia.
If you're good at talking and making chicas laugh ... you'll make many friends in person.
I'm just another geek but I have this "locura" about my personality that make chicas dig me ... except that most gringas really don't like me ... big deal :)
Suerte amigo!