I have never been to Colombia and I am enticed by the reports and photos. There are some hoy looking latinas down there!
I am ready to book a trip for mid-January, 2013 but I can not tell from the reports if I should go to Medellin or Cali. Places change over time and most of the reports are a few years old.
Any advice for a long time mongerer, first time visitor to Colombia?

Medellin...no question

Totally...MDE no doubt.

For most mongers, I would say Medellin. It's a much prettier city and the puta scene is much easier to navigate. I will say that if you speak decent Spanish and you like to dabble in the non-pro scene as well as the pros, Cali might be better.

Also, if you have an interest in Afro-Latin Music and Dance (as I do),
Cali is more than worth your time and money.

I don't know where you're used to mongering, but be prepared for
alot of silicone in both Medellin and Cali.

I haven't been to Medellin but there is plenty of info all over the net about Medellin. Beautiful city, beautiful women but maybe they are getting a little tired of gringos.
I have been to Cali, I loved it. The gringo is still a bit of a novelty there so if your Spanish is ok and you like to take few shots at non pros in the dance clubs then I would recommend Cali. Although they have lots of pro action too.
If your a lazy monger like CFK and you don't want to put too much effort into searching out the prepagos then go to Medellin.

If your a lazy monger like CFK and you don't want to put too much effort into searching out the prepagos then go to Medellin.

- I just show up and look good, that's all....

I agree with the above advice.

My first trip was to Cali. I don't speak much Spanish, and almost nobody there speaks English. Google Translate helped, but only after I got them back to the room, not in the casas. There are plenty of casas, and plenty of hot girls. The city is dangerous in places, and you should know which places before you go there. I would recommend finding a guide to help you get to the right places, taxi drivers are unreliable and greedy/crooked. If you don't speak Spanish, I wouldn't go there for your first trip.

My next two trips were to Medellin (and a day in Cali to be with a girl I liked). There are a few expats in Medellin that might help you out (I stayed with one, penthouse in a safe area, $55/night), and plenty of venues--many casas are within walking distance of each other. I believe it is safer overall (although you still have to know where not to go), certainly I felt safe walking around at night in Laureles. There seemed to be more to do/see around Medellin than Cali, but I wasn't exactly in tourist mode in Cali.

Also, Medellin features the Mansion (with which I have no experience, although many others on this board do); that sounds like a good place to stay on the first trip (even though you are experienced) to orient you to what's where etc.

To add on to Hunterman's comment about the Mansion, I think it's a great asset for the Medellin monger. If you're going down there by yourself but like to have a ready made social group, it's perfect. I've been to Mde five times and I know the scene relatively well, but I will still stay at the Mansion (or Castillo). I can't fuck 16 hours a day, and I really like the camaraderie at those two houses.

If Cali had something similar, I would definitely go back more often.